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Diffstat (limited to '')
| -rw-r--r-- | ipc/sem.c | 2464 |
1 files changed, 2464 insertions, 0 deletions
diff --git a/ipc/sem.c b/ipc/sem.c new file mode 100644 index 000000000..916f7a90b --- /dev/null +++ b/ipc/sem.c @@ -0,0 +1,2464 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/ipc/sem.c + * Copyright (C) 1992 Krishna Balasubramanian + * Copyright (C) 1995 Eric Schenk, Bruno Haible + * + * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com> + * + * SMP-threaded, sysctl's added + * (c) 1999 Manfred Spraul <manfred@colorfullife.com> + * Enforced range limit on SEM_UNDO + * (c) 2001 Red Hat Inc + * Lockless wakeup + * (c) 2003 Manfred Spraul <manfred@colorfullife.com> + * (c) 2016 Davidlohr Bueso <dave@stgolabs.net> + * Further wakeup optimizations, documentation + * (c) 2010 Manfred Spraul <manfred@colorfullife.com> + * + * support for audit of ipc object properties and permission changes + * Dustin Kirkland <dustin.kirkland@us.ibm.com> + * + * namespaces support + * OpenVZ, SWsoft Inc. + * Pavel Emelianov <xemul@openvz.org> + * + * Implementation notes: (May 2010) + * This file implements System V semaphores. + * + * User space visible behavior: + * - FIFO ordering for semop() operations (just FIFO, not starvation + * protection) + * - multiple semaphore operations that alter the same semaphore in + * one semop() are handled. + * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and + * SETALL calls. + * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO. + * - undo adjustments at process exit are limited to 0..SEMVMX. + * - namespace are supported. + * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing + * to /proc/sys/kernel/sem. + * - statistics about the usage are reported in /proc/sysvipc/sem. + * + * Internals: + * - scalability: + * - all global variables are read-mostly. + * - semop() calls and semctl(RMID) are synchronized by RCU. + * - most operations do write operations (actually: spin_lock calls) to + * the per-semaphore array structure. + * Thus: Perfect SMP scaling between independent semaphore arrays. + * If multiple semaphores in one array are used, then cache line + * trashing on the semaphore array spinlock will limit the scaling. + * - semncnt and semzcnt are calculated on demand in count_semcnt() + * - the task that performs a successful semop() scans the list of all + * sleeping tasks and completes any pending operations that can be fulfilled. + * Semaphores are actively given to waiting tasks (necessary for FIFO). + * (see update_queue()) + * - To improve the scalability, the actual wake-up calls are performed after + * dropping all locks. (see wake_up_sem_queue_prepare()) + * - All work is done by the waker, the woken up task does not have to do + * anything - not even acquiring a lock or dropping a refcount. + * - A woken up task may not even touch the semaphore array anymore, it may + * have been destroyed already by a semctl(RMID). + * - UNDO values are stored in an array (one per process and per + * semaphore array, lazily allocated). For backwards compatibility, multiple + * modes for the UNDO variables are supported (per process, per thread) + * (see copy_semundo, CLONE_SYSVSEM) + * - There are two lists of the pending operations: a per-array list + * and per-semaphore list (stored in the array). This allows to achieve FIFO + * ordering without always scanning all pending operations. + * The worst-case behavior is nevertheless O(N^2) for N wakeups. + */ + +#include <linux/compat.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/init.h> +#include <linux/proc_fs.h> +#include <linux/time.h> +#include <linux/security.h> +#include <linux/syscalls.h> +#include <linux/audit.h> +#include <linux/capability.h> +#include <linux/seq_file.h> +#include <linux/rwsem.h> +#include <linux/nsproxy.h> +#include <linux/ipc_namespace.h> +#include <linux/sched/wake_q.h> +#include <linux/nospec.h> +#include <linux/rhashtable.h> + +#include <linux/uaccess.h> +#include "util.h" + +/* One semaphore structure for each semaphore in the system. */ +struct sem { + int semval; /* current value */ + /* + * PID of the process that last modified the semaphore. For + * Linux, specifically these are: + * - semop + * - semctl, via SETVAL and SETALL. + * - at task exit when performing undo adjustments (see exit_sem). + */ + struct pid *sempid; + spinlock_t lock; /* spinlock for fine-grained semtimedop */ + struct list_head pending_alter; /* pending single-sop operations */ + /* that alter the semaphore */ + struct list_head pending_const; /* pending single-sop operations */ + /* that do not alter the semaphore*/ + time64_t sem_otime; /* candidate for sem_otime */ +} ____cacheline_aligned_in_smp; + +/* One sem_array data structure for each set of semaphores in the system. */ +struct sem_array { + struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */ + time64_t sem_ctime; /* create/last semctl() time */ + struct list_head pending_alter; /* pending operations */ + /* that alter the array */ + struct list_head pending_const; /* pending complex operations */ + /* that do not alter semvals */ + struct list_head list_id; /* undo requests on this array */ + int sem_nsems; /* no. of semaphores in array */ + int complex_count; /* pending complex operations */ + unsigned int use_global_lock;/* >0: global lock required */ + + struct sem sems[]; +} __randomize_layout; + +/* One queue for each sleeping process in the system. */ +struct sem_queue { + struct list_head list; /* queue of pending operations */ + struct task_struct *sleeper; /* this process */ + struct sem_undo *undo; /* undo structure */ + struct pid *pid; /* process id of requesting process */ + int status; /* completion status of operation */ + struct sembuf *sops; /* array of pending operations */ + struct sembuf *blocking; /* the operation that blocked */ + int nsops; /* number of operations */ + bool alter; /* does *sops alter the array? */ + bool dupsop; /* sops on more than one sem_num */ +}; + +/* Each task has a list of undo requests. They are executed automatically + * when the process exits. + */ +struct sem_undo { + struct list_head list_proc; /* per-process list: * + * all undos from one process + * rcu protected */ + struct rcu_head rcu; /* rcu struct for sem_undo */ + struct sem_undo_list *ulp; /* back ptr to sem_undo_list */ + struct list_head list_id; /* per semaphore array list: + * all undos for one array */ + int semid; /* semaphore set identifier */ + short *semadj; /* array of adjustments */ + /* one per semaphore */ +}; + +/* sem_undo_list controls shared access to the list of sem_undo structures + * that may be shared among all a CLONE_SYSVSEM task group. + */ +struct sem_undo_list { + refcount_t refcnt; + spinlock_t lock; + struct list_head list_proc; +}; + + +#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) + +static int newary(struct ipc_namespace *, struct ipc_params *); +static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); +#ifdef CONFIG_PROC_FS +static int sysvipc_sem_proc_show(struct seq_file *s, void *it); +#endif + +#define SEMMSL_FAST 256 /* 512 bytes on stack */ +#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ + +/* + * Switching from the mode suitable for simple ops + * to the mode for complex ops is costly. Therefore: + * use some hysteresis + */ +#define USE_GLOBAL_LOCK_HYSTERESIS 10 + +/* + * Locking: + * a) global sem_lock() for read/write + * sem_undo.id_next, + * sem_array.complex_count, + * sem_array.pending{_alter,_const}, + * sem_array.sem_undo + * + * b) global or semaphore sem_lock() for read/write: + * sem_array.sems[i].pending_{const,alter}: + * + * c) special: + * sem_undo_list.list_proc: + * * undo_list->lock for write + * * rcu for read + * use_global_lock: + * * global sem_lock() for write + * * either local or global sem_lock() for read. + * + * Memory ordering: + * Most ordering is enforced by using spin_lock() and spin_unlock(). + * + * Exceptions: + * 1) use_global_lock: (SEM_BARRIER_1) + * Setting it from non-zero to 0 is a RELEASE, this is ensured by + * using smp_store_release(): Immediately after setting it to 0, + * a simple op can start. + * Testing if it is non-zero is an ACQUIRE, this is ensured by using + * smp_load_acquire(). + * Setting it from 0 to non-zero must be ordered with regards to + * this smp_load_acquire(), this is guaranteed because the smp_load_acquire() + * is inside a spin_lock() and after a write from 0 to non-zero a + * spin_lock()+spin_unlock() is done. + * + * 2) queue.status: (SEM_BARRIER_2) + * Initialization is done while holding sem_lock(), so no further barrier is + * required. + * Setting it to a result code is a RELEASE, this is ensured by both a + * smp_store_release() (for case a) and while holding sem_lock() + * (for case b). + * The AQUIRE when reading the result code without holding sem_lock() is + * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep(). + * (case a above). + * Reading the result code while holding sem_lock() needs no further barriers, + * the locks inside sem_lock() enforce ordering (case b above) + * + * 3) current->state: + * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock(). + * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may + * happen immediately after calling wake_q_add. As wake_q_add_safe() is called + * when holding sem_lock(), no further barriers are required. + * + * See also ipc/mqueue.c for more details on the covered races. + */ + +#define sc_semmsl sem_ctls[0] +#define sc_semmns sem_ctls[1] +#define sc_semopm sem_ctls[2] +#define sc_semmni sem_ctls[3] + +void sem_init_ns(struct ipc_namespace *ns) +{ + ns->sc_semmsl = SEMMSL; + ns->sc_semmns = SEMMNS; + ns->sc_semopm = SEMOPM; + ns->sc_semmni = SEMMNI; + ns->used_sems = 0; + ipc_init_ids(&ns->ids[IPC_SEM_IDS]); +} + +#ifdef CONFIG_IPC_NS +void sem_exit_ns(struct ipc_namespace *ns) +{ + free_ipcs(ns, &sem_ids(ns), freeary); + idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); + rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht); +} +#endif + +void __init sem_init(void) +{ + sem_init_ns(&init_ipc_ns); + ipc_init_proc_interface("sysvipc/sem", + " key semid perms nsems uid gid cuid cgid otime ctime\n", + IPC_SEM_IDS, sysvipc_sem_proc_show); +} + +/** + * unmerge_queues - unmerge queues, if possible. + * @sma: semaphore array + * + * The function unmerges the wait queues if complex_count is 0. + * It must be called prior to dropping the global semaphore array lock. + */ +static void unmerge_queues(struct sem_array *sma) +{ + struct sem_queue *q, *tq; + + /* complex operations still around? */ + if (sma->complex_count) + return; + /* + * We will switch back to simple mode. + * Move all pending operation back into the per-semaphore + * queues. + */ + list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { + struct sem *curr; + curr = &sma->sems[q->sops[0].sem_num]; + + list_add_tail(&q->list, &curr->pending_alter); + } + INIT_LIST_HEAD(&sma->pending_alter); +} + +/** + * merge_queues - merge single semop queues into global queue + * @sma: semaphore array + * + * This function merges all per-semaphore queues into the global queue. + * It is necessary to achieve FIFO ordering for the pending single-sop + * operations when a multi-semop operation must sleep. + * Only the alter operations must be moved, the const operations can stay. + */ +static void merge_queues(struct sem_array *sma) +{ + int i; + for (i = 0; i < sma->sem_nsems; i++) { + struct sem *sem = &sma->sems[i]; + + list_splice_init(&sem->pending_alter, &sma->pending_alter); + } +} + +static void sem_rcu_free(struct rcu_head *head) +{ + struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu); + struct sem_array *sma = container_of(p, struct sem_array, sem_perm); + + security_sem_free(&sma->sem_perm); + kvfree(sma); +} + +/* + * Enter the mode suitable for non-simple operations: + * Caller must own sem_perm.lock. + */ +static void complexmode_enter(struct sem_array *sma) +{ + int i; + struct sem *sem; + + if (sma->use_global_lock > 0) { + /* + * We are already in global lock mode. + * Nothing to do, just reset the + * counter until we return to simple mode. + */ + sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; + return; + } + sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; + + for (i = 0; i < sma->sem_nsems; i++) { + sem = &sma->sems[i]; + spin_lock(&sem->lock); + spin_unlock(&sem->lock); + } +} + +/* + * Try to leave the mode that disallows simple operations: + * Caller must own sem_perm.lock. + */ +static void complexmode_tryleave(struct sem_array *sma) +{ + if (sma->complex_count) { + /* Complex ops are sleeping. + * We must stay in complex mode + */ + return; + } + if (sma->use_global_lock == 1) { + + /* See SEM_BARRIER_1 for purpose/pairing */ + smp_store_release(&sma->use_global_lock, 0); + } else { + sma->use_global_lock--; + } +} + +#define SEM_GLOBAL_LOCK (-1) +/* + * If the request contains only one semaphore operation, and there are + * no complex transactions pending, lock only the semaphore involved. + * Otherwise, lock the entire semaphore array, since we either have + * multiple semaphores in our own semops, or we need to look at + * semaphores from other pending complex operations. + */ +static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, + int nsops) +{ + struct sem *sem; + int idx; + + if (nsops != 1) { + /* Complex operation - acquire a full lock */ + ipc_lock_object(&sma->sem_perm); + + /* Prevent parallel simple ops */ + complexmode_enter(sma); + return SEM_GLOBAL_LOCK; + } + + /* + * Only one semaphore affected - try to optimize locking. + * Optimized locking is possible if no complex operation + * is either enqueued or processed right now. + * + * Both facts are tracked by use_global_mode. + */ + idx = array_index_nospec(sops->sem_num, sma->sem_nsems); + sem = &sma->sems[idx]; + + /* + * Initial check for use_global_lock. Just an optimization, + * no locking, no memory barrier. + */ + if (!sma->use_global_lock) { + /* + * It appears that no complex operation is around. + * Acquire the per-semaphore lock. + */ + spin_lock(&sem->lock); + + /* see SEM_BARRIER_1 for purpose/pairing */ + if (!smp_load_acquire(&sma->use_global_lock)) { + /* fast path successful! */ + return sops->sem_num; + } + spin_unlock(&sem->lock); + } + + /* slow path: acquire the full lock */ + ipc_lock_object(&sma->sem_perm); + + if (sma->use_global_lock == 0) { + /* + * The use_global_lock mode ended while we waited for + * sma->sem_perm.lock. Thus we must switch to locking + * with sem->lock. + * Unlike in the fast path, there is no need to recheck + * sma->use_global_lock after we have acquired sem->lock: + * We own sma->sem_perm.lock, thus use_global_lock cannot + * change. + */ + spin_lock(&sem->lock); + + ipc_unlock_object(&sma->sem_perm); + return sops->sem_num; + } else { + /* + * Not a false alarm, thus continue to use the global lock + * mode. No need for complexmode_enter(), this was done by + * the caller that has set use_global_mode to non-zero. + */ + return SEM_GLOBAL_LOCK; + } +} + +static inline void sem_unlock(struct sem_array *sma, int locknum) +{ + if (locknum == SEM_GLOBAL_LOCK) { + unmerge_queues(sma); + complexmode_tryleave(sma); + ipc_unlock_object(&sma->sem_perm); + } else { + struct sem *sem = &sma->sems[locknum]; + spin_unlock(&sem->lock); + } +} + +/* + * sem_lock_(check_) routines are called in the paths where the rwsem + * is not held. + * + * The caller holds the RCU read lock. + */ +static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) +{ + struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id); + + if (IS_ERR(ipcp)) + return ERR_CAST(ipcp); + + return container_of(ipcp, struct sem_array, sem_perm); +} + +static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns, + int id) +{ + struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id); + + if (IS_ERR(ipcp)) + return ERR_CAST(ipcp); + + return container_of(ipcp, struct sem_array, sem_perm); +} + +static inline void sem_lock_and_putref(struct sem_array *sma) +{ + sem_lock(sma, NULL, -1); + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); +} + +static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) +{ + ipc_rmid(&sem_ids(ns), &s->sem_perm); +} + +static struct sem_array *sem_alloc(size_t nsems) +{ + struct sem_array *sma; + + if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0])) + return NULL; + + sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL_ACCOUNT); + if (unlikely(!sma)) + return NULL; + + return sma; +} + +/** + * newary - Create a new semaphore set + * @ns: namespace + * @params: ptr to the structure that contains key, semflg and nsems + * + * Called with sem_ids.rwsem held (as a writer) + */ +static int newary(struct ipc_namespace *ns, struct ipc_params *params) +{ + int retval; + struct sem_array *sma; + key_t key = params->key; + int nsems = params->u.nsems; + int semflg = params->flg; + int i; + + if (!nsems) + return -EINVAL; + if (ns->used_sems + nsems > ns->sc_semmns) + return -ENOSPC; + + sma = sem_alloc(nsems); + if (!sma) + return -ENOMEM; + + sma->sem_perm.mode = (semflg & S_IRWXUGO); + sma->sem_perm.key = key; + + sma->sem_perm.security = NULL; + retval = security_sem_alloc(&sma->sem_perm); + if (retval) { + kvfree(sma); + return retval; + } + + for (i = 0; i < nsems; i++) { + INIT_LIST_HEAD(&sma->sems[i].pending_alter); + INIT_LIST_HEAD(&sma->sems[i].pending_const); + spin_lock_init(&sma->sems[i].lock); + } + + sma->complex_count = 0; + sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; + INIT_LIST_HEAD(&sma->pending_alter); + INIT_LIST_HEAD(&sma->pending_const); + INIT_LIST_HEAD(&sma->list_id); + sma->sem_nsems = nsems; + sma->sem_ctime = ktime_get_real_seconds(); + + /* ipc_addid() locks sma upon success. */ + retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); + if (retval < 0) { + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); + return retval; + } + ns->used_sems += nsems; + + sem_unlock(sma, -1); + rcu_read_unlock(); + + return sma->sem_perm.id; +} + + +/* + * Called with sem_ids.rwsem and ipcp locked. + */ +static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params) +{ + struct sem_array *sma; + + sma = container_of(ipcp, struct sem_array, sem_perm); + if (params->u.nsems > sma->sem_nsems) + return -EINVAL; + + return 0; +} + +long ksys_semget(key_t key, int nsems, int semflg) +{ + struct ipc_namespace *ns; + static const struct ipc_ops sem_ops = { + .getnew = newary, + .associate = security_sem_associate, + .more_checks = sem_more_checks, + }; + struct ipc_params sem_params; + + ns = current->nsproxy->ipc_ns; + + if (nsems < 0 || nsems > ns->sc_semmsl) + return -EINVAL; + + sem_params.key = key; + sem_params.flg = semflg; + sem_params.u.nsems = nsems; + + return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); +} + +SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) +{ + return ksys_semget(key, nsems, semflg); +} + +/** + * perform_atomic_semop[_slow] - Attempt to perform semaphore + * operations on a given array. + * @sma: semaphore array + * @q: struct sem_queue that describes the operation + * + * Caller blocking are as follows, based the value + * indicated by the semaphore operation (sem_op): + * + * (1) >0 never blocks. + * (2) 0 (wait-for-zero operation): semval is non-zero. + * (3) <0 attempting to decrement semval to a value smaller than zero. + * + * Returns 0 if the operation was possible. + * Returns 1 if the operation is impossible, the caller must sleep. + * Returns <0 for error codes. + */ +static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q) +{ + int result, sem_op, nsops; + struct pid *pid; + struct sembuf *sop; + struct sem *curr; + struct sembuf *sops; + struct sem_undo *un; + + sops = q->sops; + nsops = q->nsops; + un = q->undo; + + for (sop = sops; sop < sops + nsops; sop++) { + int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); + curr = &sma->sems[idx]; + sem_op = sop->sem_op; + result = curr->semval; + + if (!sem_op && result) + goto would_block; + + result += sem_op; + if (result < 0) + goto would_block; + if (result > SEMVMX) + goto out_of_range; + + if (sop->sem_flg & SEM_UNDO) { + int undo = un->semadj[sop->sem_num] - sem_op; + /* Exceeding the undo range is an error. */ + if (undo < (-SEMAEM - 1) || undo > SEMAEM) + goto out_of_range; + un->semadj[sop->sem_num] = undo; + } + + curr->semval = result; + } + + sop--; + pid = q->pid; + while (sop >= sops) { + ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid); + sop--; + } + + return 0; + +out_of_range: + result = -ERANGE; + goto undo; + +would_block: + q->blocking = sop; + + if (sop->sem_flg & IPC_NOWAIT) + result = -EAGAIN; + else + result = 1; + +undo: + sop--; + while (sop >= sops) { + sem_op = sop->sem_op; + sma->sems[sop->sem_num].semval -= sem_op; + if (sop->sem_flg & SEM_UNDO) + un->semadj[sop->sem_num] += sem_op; + sop--; + } + + return result; +} + +static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q) +{ + int result, sem_op, nsops; + struct sembuf *sop; + struct sem *curr; + struct sembuf *sops; + struct sem_undo *un; + + sops = q->sops; + nsops = q->nsops; + un = q->undo; + + if (unlikely(q->dupsop)) + return perform_atomic_semop_slow(sma, q); + + /* + * We scan the semaphore set twice, first to ensure that the entire + * operation can succeed, therefore avoiding any pointless writes + * to shared memory and having to undo such changes in order to block + * until the operations can go through. + */ + for (sop = sops; sop < sops + nsops; sop++) { + int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); + + curr = &sma->sems[idx]; + sem_op = sop->sem_op; + result = curr->semval; + + if (!sem_op && result) + goto would_block; /* wait-for-zero */ + + result += sem_op; + if (result < 0) + goto would_block; + + if (result > SEMVMX) + return -ERANGE; + + if (sop->sem_flg & SEM_UNDO) { + int undo = un->semadj[sop->sem_num] - sem_op; + + /* Exceeding the undo range is an error. */ + if (undo < (-SEMAEM - 1) || undo > SEMAEM) + return -ERANGE; + } + } + + for (sop = sops; sop < sops + nsops; sop++) { + curr = &sma->sems[sop->sem_num]; + sem_op = sop->sem_op; + result = curr->semval; + + if (sop->sem_flg & SEM_UNDO) { + int undo = un->semadj[sop->sem_num] - sem_op; + + un->semadj[sop->sem_num] = undo; + } + curr->semval += sem_op; + ipc_update_pid(&curr->sempid, q->pid); + } + + return 0; + +would_block: + q->blocking = sop; + return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1; +} + +static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error, + struct wake_q_head *wake_q) +{ + struct task_struct *sleeper; + + sleeper = get_task_struct(q->sleeper); + + /* see SEM_BARRIER_2 for purpuse/pairing */ + smp_store_release(&q->status, error); + + wake_q_add_safe(wake_q, sleeper); +} + +static void unlink_queue(struct sem_array *sma, struct sem_queue *q) +{ + list_del(&q->list); + if (q->nsops > 1) + sma->complex_count--; +} + +/** check_restart(sma, q) + * @sma: semaphore array + * @q: the operation that just completed + * + * update_queue is O(N^2) when it restarts scanning the whole queue of + * waiting operations. Therefore this function checks if the restart is + * really necessary. It is called after a previously waiting operation + * modified the array. + * Note that wait-for-zero operations are handled without restart. + */ +static inline int check_restart(struct sem_array *sma, struct sem_queue *q) +{ + /* pending complex alter operations are too difficult to analyse */ + if (!list_empty(&sma->pending_alter)) + return 1; + + /* we were a sleeping complex operation. Too difficult */ + if (q->nsops > 1) + return 1; + + /* It is impossible that someone waits for the new value: + * - complex operations always restart. + * - wait-for-zero are handled seperately. + * - q is a previously sleeping simple operation that + * altered the array. It must be a decrement, because + * simple increments never sleep. + * - If there are older (higher priority) decrements + * in the queue, then they have observed the original + * semval value and couldn't proceed. The operation + * decremented to value - thus they won't proceed either. + */ + return 0; +} + +/** + * wake_const_ops - wake up non-alter tasks + * @sma: semaphore array. + * @semnum: semaphore that was modified. + * @wake_q: lockless wake-queue head. + * + * wake_const_ops must be called after a semaphore in a semaphore array + * was set to 0. If complex const operations are pending, wake_const_ops must + * be called with semnum = -1, as well as with the number of each modified + * semaphore. + * The tasks that must be woken up are added to @wake_q. The return code + * is stored in q->pid. + * The function returns 1 if at least one operation was completed successfully. + */ +static int wake_const_ops(struct sem_array *sma, int semnum, + struct wake_q_head *wake_q) +{ + struct sem_queue *q, *tmp; + struct list_head *pending_list; + int semop_completed = 0; + + if (semnum == -1) + pending_list = &sma->pending_const; + else + pending_list = &sma->sems[semnum].pending_const; + + list_for_each_entry_safe(q, tmp, pending_list, list) { + int error = perform_atomic_semop(sma, q); + + if (error > 0) + continue; + /* operation completed, remove from queue & wakeup */ + unlink_queue(sma, q); + + wake_up_sem_queue_prepare(q, error, wake_q); + if (error == 0) + semop_completed = 1; + } + + return semop_completed; +} + +/** + * do_smart_wakeup_zero - wakeup all wait for zero tasks + * @sma: semaphore array + * @sops: operations that were performed + * @nsops: number of operations + * @wake_q: lockless wake-queue head + * + * Checks all required queue for wait-for-zero operations, based + * on the actual changes that were performed on the semaphore array. + * The function returns 1 if at least one operation was completed successfully. + */ +static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops, + int nsops, struct wake_q_head *wake_q) +{ + int i; + int semop_completed = 0; + int got_zero = 0; + + /* first: the per-semaphore queues, if known */ + if (sops) { + for (i = 0; i < nsops; i++) { + int num = sops[i].sem_num; + + if (sma->sems[num].semval == 0) { + got_zero = 1; + semop_completed |= wake_const_ops(sma, num, wake_q); + } + } + } else { + /* + * No sops means modified semaphores not known. + * Assume all were changed. + */ + for (i = 0; i < sma->sem_nsems; i++) { + if (sma->sems[i].semval == 0) { + got_zero = 1; + semop_completed |= wake_const_ops(sma, i, wake_q); + } + } + } + /* + * If one of the modified semaphores got 0, + * then check the global queue, too. + */ + if (got_zero) + semop_completed |= wake_const_ops(sma, -1, wake_q); + + return semop_completed; +} + + +/** + * update_queue - look for tasks that can be completed. + * @sma: semaphore array. + * @semnum: semaphore that was modified. + * @wake_q: lockless wake-queue head. + * + * update_queue must be called after a semaphore in a semaphore array + * was modified. If multiple semaphores were modified, update_queue must + * be called with semnum = -1, as well as with the number of each modified + * semaphore. + * The tasks that must be woken up are added to @wake_q. The return code + * is stored in q->pid. + * The function internally checks if const operations can now succeed. + * + * The function return 1 if at least one semop was completed successfully. + */ +static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q) +{ + struct sem_queue *q, *tmp; + struct list_head *pending_list; + int semop_completed = 0; + + if (semnum == -1) + pending_list = &sma->pending_alter; + else + pending_list = &sma->sems[semnum].pending_alter; + +again: + list_for_each_entry_safe(q, tmp, pending_list, list) { + int error, restart; + + /* If we are scanning the single sop, per-semaphore list of + * one semaphore and that semaphore is 0, then it is not + * necessary to scan further: simple increments + * that affect only one entry succeed immediately and cannot + * be in the per semaphore pending queue, and decrements + * cannot be successful if the value is already 0. + */ + if (semnum != -1 && sma->sems[semnum].semval == 0) + break; + + error = perform_atomic_semop(sma, q); + + /* Does q->sleeper still need to sleep? */ + if (error > 0) + continue; + + unlink_queue(sma, q); + + if (error) { + restart = 0; + } else { + semop_completed = 1; + do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q); + restart = check_restart(sma, q); + } + + wake_up_sem_queue_prepare(q, error, wake_q); + if (restart) + goto again; + } + return semop_completed; +} + +/** + * set_semotime - set sem_otime + * @sma: semaphore array + * @sops: operations that modified the array, may be NULL + * + * sem_otime is replicated to avoid cache line trashing. + * This function sets one instance to the current time. + */ +static void set_semotime(struct sem_array *sma, struct sembuf *sops) +{ + if (sops == NULL) { + sma->sems[0].sem_otime = ktime_get_real_seconds(); + } else { + sma->sems[sops[0].sem_num].sem_otime = + ktime_get_real_seconds(); + } +} + +/** + * do_smart_update - optimized update_queue + * @sma: semaphore array + * @sops: operations that were performed + * @nsops: number of operations + * @otime: force setting otime + * @wake_q: lockless wake-queue head + * + * do_smart_update() does the required calls to update_queue and wakeup_zero, + * based on the actual changes that were performed on the semaphore array. + * Note that the function does not do the actual wake-up: the caller is + * responsible for calling wake_up_q(). + * It is safe to perform this call after dropping all locks. + */ +static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, + int otime, struct wake_q_head *wake_q) +{ + int i; + + otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q); + + if (!list_empty(&sma->pending_alter)) { + /* semaphore array uses the global queue - just process it. */ + otime |= update_queue(sma, -1, wake_q); + } else { + if (!sops) { + /* + * No sops, thus the modified semaphores are not + * known. Check all. + */ + for (i = 0; i < sma->sem_nsems; i++) + otime |= update_queue(sma, i, wake_q); + } else { + /* + * Check the semaphores that were increased: + * - No complex ops, thus all sleeping ops are + * decrease. + * - if we decreased the value, then any sleeping + * semaphore ops wont be able to run: If the + * previous value was too small, then the new + * value will be too small, too. + */ + for (i = 0; i < nsops; i++) { + if (sops[i].sem_op > 0) { + otime |= update_queue(sma, + sops[i].sem_num, wake_q); + } + } + } + } + if (otime) + set_semotime(sma, sops); +} + +/* + * check_qop: Test if a queued operation sleeps on the semaphore semnum + */ +static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, + bool count_zero) +{ + struct sembuf *sop = q->blocking; + + /* + * Linux always (since 0.99.10) reported a task as sleeping on all + * semaphores. This violates SUS, therefore it was changed to the + * standard compliant behavior. + * Give the administrators a chance to notice that an application + * might misbehave because it relies on the Linux behavior. + */ + pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n" + "The task %s (%d) triggered the difference, watch for misbehavior.\n", + current->comm, task_pid_nr(current)); + + if (sop->sem_num != semnum) + return 0; + + if (count_zero && sop->sem_op == 0) + return 1; + if (!count_zero && sop->sem_op < 0) + return 1; + + return 0; +} + +/* The following counts are associated to each semaphore: + * semncnt number of tasks waiting on semval being nonzero + * semzcnt number of tasks waiting on semval being zero + * + * Per definition, a task waits only on the semaphore of the first semop + * that cannot proceed, even if additional operation would block, too. + */ +static int count_semcnt(struct sem_array *sma, ushort semnum, + bool count_zero) +{ + struct list_head *l; + struct sem_queue *q; + int semcnt; + + semcnt = 0; + /* First: check the simple operations. They are easy to evaluate */ + if (count_zero) + l = &sma->sems[semnum].pending_const; + else + l = &sma->sems[semnum].pending_alter; + + list_for_each_entry(q, l, list) { + /* all task on a per-semaphore list sleep on exactly + * that semaphore + */ + semcnt++; + } + + /* Then: check the complex operations. */ + list_for_each_entry(q, &sma->pending_alter, list) { + semcnt += check_qop(sma, semnum, q, count_zero); + } + if (count_zero) { + list_for_each_entry(q, &sma->pending_const, list) { + semcnt += check_qop(sma, semnum, q, count_zero); + } + } + return semcnt; +} + +/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked + * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem + * remains locked on exit. + */ +static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) +{ + struct sem_undo *un, *tu; + struct sem_queue *q, *tq; + struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); + int i; + DEFINE_WAKE_Q(wake_q); + + /* Free the existing undo structures for this semaphore set. */ + ipc_assert_locked_object(&sma->sem_perm); + list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { + list_del(&un->list_id); + spin_lock(&un->ulp->lock); + un->semid = -1; + list_del_rcu(&un->list_proc); + spin_unlock(&un->ulp->lock); + kfree_rcu(un, rcu); + } + + /* Wake up all pending processes and let them fail with EIDRM. */ + list_for_each_entry_safe(q, tq, &sma->pending_const, list) { + unlink_queue(sma, q); + wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); + } + + list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { + unlink_queue(sma, q); + wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); + } + for (i = 0; i < sma->sem_nsems; i++) { + struct sem *sem = &sma->sems[i]; + list_for_each_entry_safe(q, tq, &sem->pending_const, list) { + unlink_queue(sma, q); + wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); + } + list_for_each_entry_safe(q, tq, &sem->pending_alter, list) { + unlink_queue(sma, q); + wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); + } + ipc_update_pid(&sem->sempid, NULL); + } + + /* Remove the semaphore set from the IDR */ + sem_rmid(ns, sma); + sem_unlock(sma, -1); + rcu_read_unlock(); + + wake_up_q(&wake_q); + ns->used_sems -= sma->sem_nsems; + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); +} + +static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) +{ + switch (version) { + case IPC_64: + return copy_to_user(buf, in, sizeof(*in)); + case IPC_OLD: + { + struct semid_ds out; + + memset(&out, 0, sizeof(out)); + + ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); + + out.sem_otime = in->sem_otime; + out.sem_ctime = in->sem_ctime; + out.sem_nsems = in->sem_nsems; + + return copy_to_user(buf, &out, sizeof(out)); + } + default: + return -EINVAL; + } +} + +static time64_t get_semotime(struct sem_array *sma) +{ + int i; + time64_t res; + + res = sma->sems[0].sem_otime; + for (i = 1; i < sma->sem_nsems; i++) { + time64_t to = sma->sems[i].sem_otime; + + if (to > res) + res = to; + } + return res; +} + +static int semctl_stat(struct ipc_namespace *ns, int semid, + int cmd, struct semid64_ds *semid64) +{ + struct sem_array *sma; + time64_t semotime; + int err; + + memset(semid64, 0, sizeof(*semid64)); + + rcu_read_lock(); + if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) { + sma = sem_obtain_object(ns, semid); + if (IS_ERR(sma)) { + err = PTR_ERR(sma); + goto out_unlock; + } + } else { /* IPC_STAT */ + sma = sem_obtain_object_check(ns, semid); + if (IS_ERR(sma)) { + err = PTR_ERR(sma); + goto out_unlock; + } + } + + /* see comment for SHM_STAT_ANY */ + if (cmd == SEM_STAT_ANY) + audit_ipc_obj(&sma->sem_perm); + else { + err = -EACCES; + if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) + goto out_unlock; + } + + err = security_sem_semctl(&sma->sem_perm, cmd); + if (err) + goto out_unlock; + + ipc_lock_object(&sma->sem_perm); + + if (!ipc_valid_object(&sma->sem_perm)) { + ipc_unlock_object(&sma->sem_perm); + err = -EIDRM; + goto out_unlock; + } + + kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm); + semotime = get_semotime(sma); + semid64->sem_otime = semotime; + semid64->sem_ctime = sma->sem_ctime; +#ifndef CONFIG_64BIT + semid64->sem_otime_high = semotime >> 32; + semid64->sem_ctime_high = sma->sem_ctime >> 32; +#endif + semid64->sem_nsems = sma->sem_nsems; + + if (cmd == IPC_STAT) { + /* + * As defined in SUS: + * Return 0 on success + */ + err = 0; + } else { + /* + * SEM_STAT and SEM_STAT_ANY (both Linux specific) + * Return the full id, including the sequence number + */ + err = sma->sem_perm.id; + } + ipc_unlock_object(&sma->sem_perm); +out_unlock: + rcu_read_unlock(); + return err; +} + +static int semctl_info(struct ipc_namespace *ns, int semid, + int cmd, void __user *p) +{ + struct seminfo seminfo; + int max_idx; + int err; + + err = security_sem_semctl(NULL, cmd); + if (err) + return err; + + memset(&seminfo, 0, sizeof(seminfo)); + seminfo.semmni = ns->sc_semmni; + seminfo.semmns = ns->sc_semmns; + seminfo.semmsl = ns->sc_semmsl; + seminfo.semopm = ns->sc_semopm; + seminfo.semvmx = SEMVMX; + seminfo.semmnu = SEMMNU; + seminfo.semmap = SEMMAP; + seminfo.semume = SEMUME; + down_read(&sem_ids(ns).rwsem); + if (cmd == SEM_INFO) { + seminfo.semusz = sem_ids(ns).in_use; + seminfo.semaem = ns->used_sems; + } else { + seminfo.semusz = SEMUSZ; + seminfo.semaem = SEMAEM; + } + max_idx = ipc_get_maxidx(&sem_ids(ns)); + up_read(&sem_ids(ns).rwsem); + if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) + return -EFAULT; + return (max_idx < 0) ? 0 : max_idx; +} + +static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, + int val) +{ + struct sem_undo *un; + struct sem_array *sma; + struct sem *curr; + int err; + DEFINE_WAKE_Q(wake_q); + + if (val > SEMVMX || val < 0) + return -ERANGE; + + rcu_read_lock(); + sma = sem_obtain_object_check(ns, semid); + if (IS_ERR(sma)) { + rcu_read_unlock(); + return PTR_ERR(sma); + } + + if (semnum < 0 || semnum >= sma->sem_nsems) { + rcu_read_unlock(); + return -EINVAL; + } + + + if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) { + rcu_read_unlock(); + return -EACCES; + } + + err = security_sem_semctl(&sma->sem_perm, SETVAL); + if (err) { + rcu_read_unlock(); + return -EACCES; + } + + sem_lock(sma, NULL, -1); + + if (!ipc_valid_object(&sma->sem_perm)) { + sem_unlock(sma, -1); + rcu_read_unlock(); + return -EIDRM; + } + + semnum = array_index_nospec(semnum, sma->sem_nsems); + curr = &sma->sems[semnum]; + + ipc_assert_locked_object(&sma->sem_perm); + list_for_each_entry(un, &sma->list_id, list_id) + un->semadj[semnum] = 0; + + curr->semval = val; + ipc_update_pid(&curr->sempid, task_tgid(current)); + sma->sem_ctime = ktime_get_real_seconds(); + /* maybe some queued-up processes were waiting for this */ + do_smart_update(sma, NULL, 0, 0, &wake_q); + sem_unlock(sma, -1); + rcu_read_unlock(); + wake_up_q(&wake_q); + return 0; +} + +static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, + int cmd, void __user *p) +{ + struct sem_array *sma; + struct sem *curr; + int err, nsems; + ushort fast_sem_io[SEMMSL_FAST]; + ushort *sem_io = fast_sem_io; + DEFINE_WAKE_Q(wake_q); + + rcu_read_lock(); + sma = sem_obtain_object_check(ns, semid); + if (IS_ERR(sma)) { + rcu_read_unlock(); + return PTR_ERR(sma); + } + + nsems = sma->sem_nsems; + + err = -EACCES; + if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO)) + goto out_rcu_wakeup; + + err = security_sem_semctl(&sma->sem_perm, cmd); + if (err) + goto out_rcu_wakeup; + + err = -EACCES; + switch (cmd) { + case GETALL: + { + ushort __user *array = p; + int i; + + sem_lock(sma, NULL, -1); + if (!ipc_valid_object(&sma->sem_perm)) { + err = -EIDRM; + goto out_unlock; + } + if (nsems > SEMMSL_FAST) { + if (!ipc_rcu_getref(&sma->sem_perm)) { + err = -EIDRM; + goto out_unlock; + } + sem_unlock(sma, -1); + rcu_read_unlock(); + sem_io = kvmalloc_array(nsems, sizeof(ushort), + GFP_KERNEL); + if (sem_io == NULL) { + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); + return -ENOMEM; + } + + rcu_read_lock(); + sem_lock_and_putref(sma); + if (!ipc_valid_object(&sma->sem_perm)) { + err = -EIDRM; + goto out_unlock; + } + } + for (i = 0; i < sma->sem_nsems; i++) + sem_io[i] = sma->sems[i].semval; + sem_unlock(sma, -1); + rcu_read_unlock(); + err = 0; + if (copy_to_user(array, sem_io, nsems*sizeof(ushort))) + err = -EFAULT; + goto out_free; + } + case SETALL: + { + int i; + struct sem_undo *un; + + if (!ipc_rcu_getref(&sma->sem_perm)) { + err = -EIDRM; + goto out_rcu_wakeup; + } + rcu_read_unlock(); + + if (nsems > SEMMSL_FAST) { + sem_io = kvmalloc_array(nsems, sizeof(ushort), + GFP_KERNEL); + if (sem_io == NULL) { + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); + return -ENOMEM; + } + } + + if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) { + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); + err = -EFAULT; + goto out_free; + } + + for (i = 0; i < nsems; i++) { + if (sem_io[i] > SEMVMX) { + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); + err = -ERANGE; + goto out_free; + } + } + rcu_read_lock(); + sem_lock_and_putref(sma); + if (!ipc_valid_object(&sma->sem_perm)) { + err = -EIDRM; + goto out_unlock; + } + + for (i = 0; i < nsems; i++) { + sma->sems[i].semval = sem_io[i]; + ipc_update_pid(&sma->sems[i].sempid, task_tgid(current)); + } + + ipc_assert_locked_object(&sma->sem_perm); + list_for_each_entry(un, &sma->list_id, list_id) { + for (i = 0; i < nsems; i++) + un->semadj[i] = 0; + } + sma->sem_ctime = ktime_get_real_seconds(); + /* maybe some queued-up processes were waiting for this */ + do_smart_update(sma, NULL, 0, 0, &wake_q); + err = 0; + goto out_unlock; + } + /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */ + } + err = -EINVAL; + if (semnum < 0 || semnum >= nsems) + goto out_rcu_wakeup; + + sem_lock(sma, NULL, -1); + if (!ipc_valid_object(&sma->sem_perm)) { + err = -EIDRM; + goto out_unlock; + } + + semnum = array_index_nospec(semnum, nsems); + curr = &sma->sems[semnum]; + + switch (cmd) { + case GETVAL: + err = curr->semval; + goto out_unlock; + case GETPID: + err = pid_vnr(curr->sempid); + goto out_unlock; + case GETNCNT: + err = count_semcnt(sma, semnum, 0); + goto out_unlock; + case GETZCNT: + err = count_semcnt(sma, semnum, 1); + goto out_unlock; + } + +out_unlock: + sem_unlock(sma, -1); +out_rcu_wakeup: + rcu_read_unlock(); + wake_up_q(&wake_q); +out_free: + if (sem_io != fast_sem_io) + kvfree(sem_io); + return err; +} + +static inline unsigned long +copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) +{ + switch (version) { + case IPC_64: + if (copy_from_user(out, buf, sizeof(*out))) + return -EFAULT; + return 0; + case IPC_OLD: + { + struct semid_ds tbuf_old; + + if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) + return -EFAULT; + + out->sem_perm.uid = tbuf_old.sem_perm.uid; + out->sem_perm.gid = tbuf_old.sem_perm.gid; + out->sem_perm.mode = tbuf_old.sem_perm.mode; + + return 0; + } + default: + return -EINVAL; + } +} + +/* + * This function handles some semctl commands which require the rwsem + * to be held in write mode. + * NOTE: no locks must be held, the rwsem is taken inside this function. + */ +static int semctl_down(struct ipc_namespace *ns, int semid, + int cmd, struct semid64_ds *semid64) +{ + struct sem_array *sma; + int err; + struct kern_ipc_perm *ipcp; + + down_write(&sem_ids(ns).rwsem); + rcu_read_lock(); + + ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd, + &semid64->sem_perm, 0); + if (IS_ERR(ipcp)) { + err = PTR_ERR(ipcp); + goto out_unlock1; + } + + sma = container_of(ipcp, struct sem_array, sem_perm); + + err = security_sem_semctl(&sma->sem_perm, cmd); + if (err) + goto out_unlock1; + + switch (cmd) { + case IPC_RMID: + sem_lock(sma, NULL, -1); + /* freeary unlocks the ipc object and rcu */ + freeary(ns, ipcp); + goto out_up; + case IPC_SET: + sem_lock(sma, NULL, -1); + err = ipc_update_perm(&semid64->sem_perm, ipcp); + if (err) + goto out_unlock0; + sma->sem_ctime = ktime_get_real_seconds(); + break; + default: + err = -EINVAL; + goto out_unlock1; + } + +out_unlock0: + sem_unlock(sma, -1); +out_unlock1: + rcu_read_unlock(); +out_up: + up_write(&sem_ids(ns).rwsem); + return err; +} + +static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version) +{ + struct ipc_namespace *ns; + void __user *p = (void __user *)arg; + struct semid64_ds semid64; + int err; + + if (semid < 0) + return -EINVAL; + + ns = current->nsproxy->ipc_ns; + + switch (cmd) { + case IPC_INFO: + case SEM_INFO: + return semctl_info(ns, semid, cmd, p); + case IPC_STAT: + case SEM_STAT: + case SEM_STAT_ANY: + err = semctl_stat(ns, semid, cmd, &semid64); + if (err < 0) + return err; + if (copy_semid_to_user(p, &semid64, version)) + err = -EFAULT; + return err; + case GETALL: + case GETVAL: + case GETPID: + case GETNCNT: + case GETZCNT: + case SETALL: + return semctl_main(ns, semid, semnum, cmd, p); + case SETVAL: { + int val; +#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN) + /* big-endian 64bit */ + val = arg >> 32; +#else + /* 32bit or little-endian 64bit */ + val = arg; +#endif + return semctl_setval(ns, semid, semnum, val); + } + case IPC_SET: + if (copy_semid_from_user(&semid64, p, version)) + return -EFAULT; + fallthrough; + case IPC_RMID: + return semctl_down(ns, semid, cmd, &semid64); + default: + return -EINVAL; + } +} + +SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) +{ + return ksys_semctl(semid, semnum, cmd, arg, IPC_64); +} + +#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION +long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg) +{ + int version = ipc_parse_version(&cmd); + + return ksys_semctl(semid, semnum, cmd, arg, version); +} + +SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) +{ + return ksys_old_semctl(semid, semnum, cmd, arg); +} +#endif + +#ifdef CONFIG_COMPAT + +struct compat_semid_ds { + struct compat_ipc_perm sem_perm; + old_time32_t sem_otime; + old_time32_t sem_ctime; + compat_uptr_t sem_base; + compat_uptr_t sem_pending; + compat_uptr_t sem_pending_last; + compat_uptr_t undo; + unsigned short sem_nsems; +}; + +static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf, + int version) +{ + memset(out, 0, sizeof(*out)); + if (version == IPC_64) { + struct compat_semid64_ds __user *p = buf; + return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm); + } else { + struct compat_semid_ds __user *p = buf; + return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm); + } +} + +static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in, + int version) +{ + if (version == IPC_64) { + struct compat_semid64_ds v; + memset(&v, 0, sizeof(v)); + to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm); + v.sem_otime = lower_32_bits(in->sem_otime); + v.sem_otime_high = upper_32_bits(in->sem_otime); + v.sem_ctime = lower_32_bits(in->sem_ctime); + v.sem_ctime_high = upper_32_bits(in->sem_ctime); + v.sem_nsems = in->sem_nsems; + return copy_to_user(buf, &v, sizeof(v)); + } else { + struct compat_semid_ds v; + memset(&v, 0, sizeof(v)); + to_compat_ipc_perm(&v.sem_perm, &in->sem_perm); + v.sem_otime = in->sem_otime; + v.sem_ctime = in->sem_ctime; + v.sem_nsems = in->sem_nsems; + return copy_to_user(buf, &v, sizeof(v)); + } +} + +static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version) +{ + void __user *p = compat_ptr(arg); + struct ipc_namespace *ns; + struct semid64_ds semid64; + int err; + + ns = current->nsproxy->ipc_ns; + + if (semid < 0) + return -EINVAL; + + switch (cmd & (~IPC_64)) { + case IPC_INFO: + case SEM_INFO: + return semctl_info(ns, semid, cmd, p); + case IPC_STAT: + case SEM_STAT: + case SEM_STAT_ANY: + err = semctl_stat(ns, semid, cmd, &semid64); + if (err < 0) + return err; + if (copy_compat_semid_to_user(p, &semid64, version)) + err = -EFAULT; + return err; + case GETVAL: + case GETPID: + case GETNCNT: + case GETZCNT: + case GETALL: + case SETALL: + return semctl_main(ns, semid, semnum, cmd, p); + case SETVAL: + return semctl_setval(ns, semid, semnum, arg); + case IPC_SET: + if (copy_compat_semid_from_user(&semid64, p, version)) + return -EFAULT; + fallthrough; + case IPC_RMID: + return semctl_down(ns, semid, cmd, &semid64); + default: + return -EINVAL; + } +} + +COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg) +{ + return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64); +} + +#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION +long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg) +{ + int version = compat_ipc_parse_version(&cmd); + + return compat_ksys_semctl(semid, semnum, cmd, arg, version); +} + +COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg) +{ + return compat_ksys_old_semctl(semid, semnum, cmd, arg); +} +#endif +#endif + +/* If the task doesn't already have a undo_list, then allocate one + * here. We guarantee there is only one thread using this undo list, + * and current is THE ONE + * + * If this allocation and assignment succeeds, but later + * portions of this code fail, there is no need to free the sem_undo_list. + * Just let it stay associated with the task, and it'll be freed later + * at exit time. + * + * This can block, so callers must hold no locks. + */ +static inline int get_undo_list(struct sem_undo_list **undo_listp) +{ + struct sem_undo_list *undo_list; + + undo_list = current->sysvsem.undo_list; + if (!undo_list) { + undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL_ACCOUNT); + if (undo_list == NULL) + return -ENOMEM; + spin_lock_init(&undo_list->lock); + refcount_set(&undo_list->refcnt, 1); + INIT_LIST_HEAD(&undo_list->list_proc); + + current->sysvsem.undo_list = undo_list; + } + *undo_listp = undo_list; + return 0; +} + +static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) +{ + struct sem_undo *un; + + list_for_each_entry_rcu(un, &ulp->list_proc, list_proc, + spin_is_locked(&ulp->lock)) { + if (un->semid == semid) + return un; + } + return NULL; +} + +static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) +{ + struct sem_undo *un; + + assert_spin_locked(&ulp->lock); + + un = __lookup_undo(ulp, semid); + if (un) { + list_del_rcu(&un->list_proc); + list_add_rcu(&un->list_proc, &ulp->list_proc); + } + return un; +} + +/** + * find_alloc_undo - lookup (and if not present create) undo array + * @ns: namespace + * @semid: semaphore array id + * + * The function looks up (and if not present creates) the undo structure. + * The size of the undo structure depends on the size of the semaphore + * array, thus the alloc path is not that straightforward. + * Lifetime-rules: sem_undo is rcu-protected, on success, the function + * performs a rcu_read_lock(). + */ +static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) +{ + struct sem_array *sma; + struct sem_undo_list *ulp; + struct sem_undo *un, *new; + int nsems, error; + + error = get_undo_list(&ulp); + if (error) + return ERR_PTR(error); + + rcu_read_lock(); + spin_lock(&ulp->lock); + un = lookup_undo(ulp, semid); + spin_unlock(&ulp->lock); + if (likely(un != NULL)) + goto out; + + /* no undo structure around - allocate one. */ + /* step 1: figure out the size of the semaphore array */ + sma = sem_obtain_object_check(ns, semid); + if (IS_ERR(sma)) { + rcu_read_unlock(); + return ERR_CAST(sma); + } + + nsems = sma->sem_nsems; + if (!ipc_rcu_getref(&sma->sem_perm)) { + rcu_read_unlock(); + un = ERR_PTR(-EIDRM); + goto out; + } + rcu_read_unlock(); + + /* step 2: allocate new undo structure */ + new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL_ACCOUNT); + if (!new) { + ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); + return ERR_PTR(-ENOMEM); + } + + /* step 3: Acquire the lock on semaphore array */ + rcu_read_lock(); + sem_lock_and_putref(sma); + if (!ipc_valid_object(&sma->sem_perm)) { + sem_unlock(sma, -1); + rcu_read_unlock(); + kfree(new); + un = ERR_PTR(-EIDRM); + goto out; + } + spin_lock(&ulp->lock); + + /* + * step 4: check for races: did someone else allocate the undo struct? + */ + un = lookup_undo(ulp, semid); + if (un) { + kfree(new); + goto success; + } + /* step 5: initialize & link new undo structure */ + new->semadj = (short *) &new[1]; + new->ulp = ulp; + new->semid = semid; + assert_spin_locked(&ulp->lock); + list_add_rcu(&new->list_proc, &ulp->list_proc); + ipc_assert_locked_object(&sma->sem_perm); + list_add(&new->list_id, &sma->list_id); + un = new; + +success: + spin_unlock(&ulp->lock); + sem_unlock(sma, -1); +out: + return un; +} + +static long do_semtimedop(int semid, struct sembuf __user *tsops, + unsigned nsops, const struct timespec64 *timeout) +{ + int error = -EINVAL; + struct sem_array *sma; + struct sembuf fast_sops[SEMOPM_FAST]; + struct sembuf *sops = fast_sops, *sop; + struct sem_undo *un; + int max, locknum; + bool undos = false, alter = false, dupsop = false; + struct sem_queue queue; + unsigned long dup = 0, jiffies_left = 0; + struct ipc_namespace *ns; + + ns = current->nsproxy->ipc_ns; + + if (nsops < 1 || semid < 0) + return -EINVAL; + if (nsops > ns->sc_semopm) + return -E2BIG; + if (nsops > SEMOPM_FAST) { + sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL); + if (sops == NULL) + return -ENOMEM; + } + + if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) { + error = -EFAULT; + goto out_free; + } + + if (timeout) { + if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 || + timeout->tv_nsec >= 1000000000L) { + error = -EINVAL; + goto out_free; + } + jiffies_left = timespec64_to_jiffies(timeout); + } + + max = 0; + for (sop = sops; sop < sops + nsops; sop++) { + unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG); + + if (sop->sem_num >= max) + max = sop->sem_num; + if (sop->sem_flg & SEM_UNDO) + undos = true; + if (dup & mask) { + /* + * There was a previous alter access that appears + * to have accessed the same semaphore, thus use + * the dupsop logic. "appears", because the detection + * can only check % BITS_PER_LONG. + */ + dupsop = true; + } + if (sop->sem_op != 0) { + alter = true; + dup |= mask; + } + } + + if (undos) { + /* On success, find_alloc_undo takes the rcu_read_lock */ + un = find_alloc_undo(ns, semid); + if (IS_ERR(un)) { + error = PTR_ERR(un); + goto out_free; + } + } else { + un = NULL; + rcu_read_lock(); + } + + sma = sem_obtain_object_check(ns, semid); + if (IS_ERR(sma)) { + rcu_read_unlock(); + error = PTR_ERR(sma); + goto out_free; + } + + error = -EFBIG; + if (max >= sma->sem_nsems) { + rcu_read_unlock(); + goto out_free; + } + + error = -EACCES; + if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) { + rcu_read_unlock(); + goto out_free; + } + + error = security_sem_semop(&sma->sem_perm, sops, nsops, alter); + if (error) { + rcu_read_unlock(); + goto out_free; + } + + error = -EIDRM; + locknum = sem_lock(sma, sops, nsops); + /* + * We eventually might perform the following check in a lockless + * fashion, considering ipc_valid_object() locking constraints. + * If nsops == 1 and there is no contention for sem_perm.lock, then + * only a per-semaphore lock is held and it's OK to proceed with the + * check below. More details on the fine grained locking scheme + * entangled here and why it's RMID race safe on comments at sem_lock() + */ + if (!ipc_valid_object(&sma->sem_perm)) + goto out_unlock_free; + /* + * semid identifiers are not unique - find_alloc_undo may have + * allocated an undo structure, it was invalidated by an RMID + * and now a new array with received the same id. Check and fail. + * This case can be detected checking un->semid. The existence of + * "un" itself is guaranteed by rcu. + */ + if (un && un->semid == -1) + goto out_unlock_free; + + queue.sops = sops; + queue.nsops = nsops; + queue.undo = un; + queue.pid = task_tgid(current); + queue.alter = alter; + queue.dupsop = dupsop; + + error = perform_atomic_semop(sma, &queue); + if (error == 0) { /* non-blocking succesfull path */ + DEFINE_WAKE_Q(wake_q); + + /* + * If the operation was successful, then do + * the required updates. + */ + if (alter) + do_smart_update(sma, sops, nsops, 1, &wake_q); + else + set_semotime(sma, sops); + + sem_unlock(sma, locknum); + rcu_read_unlock(); + wake_up_q(&wake_q); + + goto out_free; + } + if (error < 0) /* non-blocking error path */ + goto out_unlock_free; + + /* + * We need to sleep on this operation, so we put the current + * task into the pending queue and go to sleep. + */ + if (nsops == 1) { + struct sem *curr; + int idx = array_index_nospec(sops->sem_num, sma->sem_nsems); + curr = &sma->sems[idx]; + + if (alter) { + if (sma->complex_count) { + list_add_tail(&queue.list, + &sma->pending_alter); + } else { + + list_add_tail(&queue.list, + &curr->pending_alter); + } + } else { + list_add_tail(&queue.list, &curr->pending_const); + } + } else { + if (!sma->complex_count) + merge_queues(sma); + + if (alter) + list_add_tail(&queue.list, &sma->pending_alter); + else + list_add_tail(&queue.list, &sma->pending_const); + + sma->complex_count++; + } + + do { + /* memory ordering ensured by the lock in sem_lock() */ + WRITE_ONCE(queue.status, -EINTR); + queue.sleeper = current; + + /* memory ordering is ensured by the lock in sem_lock() */ + __set_current_state(TASK_INTERRUPTIBLE); + sem_unlock(sma, locknum); + rcu_read_unlock(); + + if (timeout) + jiffies_left = schedule_timeout(jiffies_left); + else + schedule(); + + /* + * fastpath: the semop has completed, either successfully or + * not, from the syscall pov, is quite irrelevant to us at this + * point; we're done. + * + * We _do_ care, nonetheless, about being awoken by a signal or + * spuriously. The queue.status is checked again in the + * slowpath (aka after taking sem_lock), such that we can detect + * scenarios where we were awakened externally, during the + * window between wake_q_add() and wake_up_q(). + */ + rcu_read_lock(); + error = READ_ONCE(queue.status); + if (error != -EINTR) { + /* see SEM_BARRIER_2 for purpose/pairing */ + smp_acquire__after_ctrl_dep(); + rcu_read_unlock(); + goto out_free; + } + + locknum = sem_lock(sma, sops, nsops); + + if (!ipc_valid_object(&sma->sem_perm)) + goto out_unlock_free; + + /* + * No necessity for any barrier: We are protect by sem_lock() + */ + error = READ_ONCE(queue.status); + + /* + * If queue.status != -EINTR we are woken up by another process. + * Leave without unlink_queue(), but with sem_unlock(). + */ + if (error != -EINTR) + goto out_unlock_free; + + /* + * If an interrupt occurred we have to clean up the queue. + */ + if (timeout && jiffies_left == 0) + error = -EAGAIN; + } while (error == -EINTR && !signal_pending(current)); /* spurious */ + + unlink_queue(sma, &queue); + +out_unlock_free: + sem_unlock(sma, locknum); + rcu_read_unlock(); +out_free: + if (sops != fast_sops) + kvfree(sops); + return error; +} + +long ksys_semtimedop(int semid, struct sembuf __user *tsops, + unsigned int nsops, const struct __kernel_timespec __user *timeout) +{ + if (timeout) { + struct timespec64 ts; + if (get_timespec64(&ts, timeout)) + return -EFAULT; + return do_semtimedop(semid, tsops, nsops, &ts); + } + return do_semtimedop(semid, tsops, nsops, NULL); +} + +SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, + unsigned int, nsops, const struct __kernel_timespec __user *, timeout) +{ + return ksys_semtimedop(semid, tsops, nsops, timeout); +} + +#ifdef CONFIG_COMPAT_32BIT_TIME +long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems, + unsigned int nsops, + const struct old_timespec32 __user *timeout) +{ + if (timeout) { + struct timespec64 ts; + if (get_old_timespec32(&ts, timeout)) + return -EFAULT; + return do_semtimedop(semid, tsems, nsops, &ts); + } + return do_semtimedop(semid, tsems, nsops, NULL); +} + +SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems, + unsigned int, nsops, + const struct old_timespec32 __user *, timeout) +{ + return compat_ksys_semtimedop(semid, tsems, nsops, timeout); +} +#endif + +SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, + unsigned, nsops) +{ + return do_semtimedop(semid, tsops, nsops, NULL); +} + +/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between + * parent and child tasks. + */ + +int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) +{ + struct sem_undo_list *undo_list; + int error; + + if (clone_flags & CLONE_SYSVSEM) { + error = get_undo_list(&undo_list); + if (error) + return error; + refcount_inc(&undo_list->refcnt); + tsk->sysvsem.undo_list = undo_list; + } else + tsk->sysvsem.undo_list = NULL; + + return 0; +} + +/* + * add semadj values to semaphores, free undo structures. + * undo structures are not freed when semaphore arrays are destroyed + * so some of them may be out of date. + * IMPLEMENTATION NOTE: There is some confusion over whether the + * set of adjustments that needs to be done should be done in an atomic + * manner or not. That is, if we are attempting to decrement the semval + * should we queue up and wait until we can do so legally? + * The original implementation attempted to do this (queue and wait). + * The current implementation does not do so. The POSIX standard + * and SVID should be consulted to determine what behavior is mandated. + */ +void exit_sem(struct task_struct *tsk) +{ + struct sem_undo_list *ulp; + + ulp = tsk->sysvsem.undo_list; + if (!ulp) + return; + tsk->sysvsem.undo_list = NULL; + + if (!refcount_dec_and_test(&ulp->refcnt)) + return; + + for (;;) { + struct sem_array *sma; + struct sem_undo *un; + int semid, i; + DEFINE_WAKE_Q(wake_q); + + cond_resched(); + + rcu_read_lock(); + un = list_entry_rcu(ulp->list_proc.next, + struct sem_undo, list_proc); + if (&un->list_proc == &ulp->list_proc) { + /* + * We must wait for freeary() before freeing this ulp, + * in case we raced with last sem_undo. There is a small + * possibility where we exit while freeary() didn't + * finish unlocking sem_undo_list. + */ + spin_lock(&ulp->lock); + spin_unlock(&ulp->lock); + rcu_read_unlock(); + break; + } + spin_lock(&ulp->lock); + semid = un->semid; + spin_unlock(&ulp->lock); + + /* exit_sem raced with IPC_RMID, nothing to do */ + if (semid == -1) { + rcu_read_unlock(); + continue; + } + + sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid); + /* exit_sem raced with IPC_RMID, nothing to do */ + if (IS_ERR(sma)) { + rcu_read_unlock(); + continue; + } + + sem_lock(sma, NULL, -1); + /* exit_sem raced with IPC_RMID, nothing to do */ + if (!ipc_valid_object(&sma->sem_perm)) { + sem_unlock(sma, -1); + rcu_read_unlock(); + continue; + } + un = __lookup_undo(ulp, semid); + if (un == NULL) { + /* exit_sem raced with IPC_RMID+semget() that created + * exactly the same semid. Nothing to do. + */ + sem_unlock(sma, -1); + rcu_read_unlock(); + continue; + } + + /* remove un from the linked lists */ + ipc_assert_locked_object(&sma->sem_perm); + list_del(&un->list_id); + + spin_lock(&ulp->lock); + list_del_rcu(&un->list_proc); + spin_unlock(&ulp->lock); + + /* perform adjustments registered in un */ + for (i = 0; i < sma->sem_nsems; i++) { + struct sem *semaphore = &sma->sems[i]; + if (un->semadj[i]) { + semaphore->semval += un->semadj[i]; + /* + * Range checks of the new semaphore value, + * not defined by sus: + * - Some unices ignore the undo entirely + * (e.g. HP UX 11i 11.22, Tru64 V5.1) + * - some cap the value (e.g. FreeBSD caps + * at 0, but doesn't enforce SEMVMX) + * + * Linux caps the semaphore value, both at 0 + * and at SEMVMX. + * + * Manfred <manfred@colorfullife.com> + */ + if (semaphore->semval < 0) + semaphore->semval = 0; + if (semaphore->semval > SEMVMX) + semaphore->semval = SEMVMX; + ipc_update_pid(&semaphore->sempid, task_tgid(current)); + } + } + /* maybe some queued-up processes were waiting for this */ + do_smart_update(sma, NULL, 0, 1, &wake_q); + sem_unlock(sma, -1); + rcu_read_unlock(); + wake_up_q(&wake_q); + + kfree_rcu(un, rcu); + } + kfree(ulp); +} + +#ifdef CONFIG_PROC_FS +static int sysvipc_sem_proc_show(struct seq_file *s, void *it) +{ + struct user_namespace *user_ns = seq_user_ns(s); + struct kern_ipc_perm *ipcp = it; + struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); + time64_t sem_otime; + + /* + * The proc interface isn't aware of sem_lock(), it calls + * ipc_lock_object() directly (in sysvipc_find_ipc). + * In order to stay compatible with sem_lock(), we must + * enter / leave complex_mode. + */ + complexmode_enter(sma); + + sem_otime = get_semotime(sma); + + seq_printf(s, + "%10d %10d %4o %10u %5u %5u %5u %5u %10llu %10llu\n", + sma->sem_perm.key, + sma->sem_perm.id, + sma->sem_perm.mode, + sma->sem_nsems, + from_kuid_munged(user_ns, sma->sem_perm.uid), + from_kgid_munged(user_ns, sma->sem_perm.gid), + from_kuid_munged(user_ns, sma->sem_perm.cuid), + from_kgid_munged(user_ns, sma->sem_perm.cgid), + sem_otime, + sma->sem_ctime); + + complexmode_tryleave(sma); + + return 0; +} +#endif |