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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /kernel/user.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'kernel/user.c')
-rw-r--r--kernel/user.c252
1 files changed, 252 insertions, 0 deletions
diff --git a/kernel/user.c b/kernel/user.c
new file mode 100644
index 0000000000..d667debeaf
--- /dev/null
+++ b/kernel/user.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * The "user cache".
+ *
+ * (C) Copyright 1991-2000 Linus Torvalds
+ *
+ * We have a per-user structure to keep track of how many
+ * processes, files etc the user has claimed, in order to be
+ * able to have per-user limits for system resources.
+ */
+
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/key.h>
+#include <linux/sched/user.h>
+#include <linux/interrupt.h>
+#include <linux/export.h>
+#include <linux/user_namespace.h>
+#include <linux/proc_ns.h>
+
+/*
+ * userns count is 1 for root user, 1 for init_uts_ns,
+ * and 1 for... ?
+ */
+struct user_namespace init_user_ns = {
+ .uid_map = {
+ .nr_extents = 1,
+ {
+ .extent[0] = {
+ .first = 0,
+ .lower_first = 0,
+ .count = 4294967295U,
+ },
+ },
+ },
+ .gid_map = {
+ .nr_extents = 1,
+ {
+ .extent[0] = {
+ .first = 0,
+ .lower_first = 0,
+ .count = 4294967295U,
+ },
+ },
+ },
+ .projid_map = {
+ .nr_extents = 1,
+ {
+ .extent[0] = {
+ .first = 0,
+ .lower_first = 0,
+ .count = 4294967295U,
+ },
+ },
+ },
+ .ns.count = REFCOUNT_INIT(3),
+ .owner = GLOBAL_ROOT_UID,
+ .group = GLOBAL_ROOT_GID,
+ .ns.inum = PROC_USER_INIT_INO,
+#ifdef CONFIG_USER_NS
+ .ns.ops = &userns_operations,
+#endif
+ .flags = USERNS_INIT_FLAGS,
+#ifdef CONFIG_KEYS
+ .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list),
+ .keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem),
+#endif
+};
+EXPORT_SYMBOL_GPL(init_user_ns);
+
+/*
+ * UID task count cache, to get fast user lookup in "alloc_uid"
+ * when changing user ID's (ie setuid() and friends).
+ */
+
+#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
+#define UIDHASH_SZ (1 << UIDHASH_BITS)
+#define UIDHASH_MASK (UIDHASH_SZ - 1)
+#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
+#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
+
+static struct kmem_cache *uid_cachep;
+static struct hlist_head uidhash_table[UIDHASH_SZ];
+
+/*
+ * The uidhash_lock is mostly taken from process context, but it is
+ * occasionally also taken from softirq/tasklet context, when
+ * task-structs get RCU-freed. Hence all locking must be softirq-safe.
+ * But free_uid() is also called with local interrupts disabled, and running
+ * local_bh_enable() with local interrupts disabled is an error - we'll run
+ * softirq callbacks, and they can unconditionally enable interrupts, and
+ * the caller of free_uid() didn't expect that..
+ */
+static DEFINE_SPINLOCK(uidhash_lock);
+
+/* root_user.__count is 1, for init task cred */
+struct user_struct root_user = {
+ .__count = REFCOUNT_INIT(1),
+ .uid = GLOBAL_ROOT_UID,
+ .ratelimit = RATELIMIT_STATE_INIT(root_user.ratelimit, 0, 0),
+};
+
+/*
+ * These routines must be called with the uidhash spinlock held!
+ */
+static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
+{
+ hlist_add_head(&up->uidhash_node, hashent);
+}
+
+static void uid_hash_remove(struct user_struct *up)
+{
+ hlist_del_init(&up->uidhash_node);
+}
+
+static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
+{
+ struct user_struct *user;
+
+ hlist_for_each_entry(user, hashent, uidhash_node) {
+ if (uid_eq(user->uid, uid)) {
+ refcount_inc(&user->__count);
+ return user;
+ }
+ }
+
+ return NULL;
+}
+
+static int user_epoll_alloc(struct user_struct *up)
+{
+#ifdef CONFIG_EPOLL
+ return percpu_counter_init(&up->epoll_watches, 0, GFP_KERNEL);
+#else
+ return 0;
+#endif
+}
+
+static void user_epoll_free(struct user_struct *up)
+{
+#ifdef CONFIG_EPOLL
+ percpu_counter_destroy(&up->epoll_watches);
+#endif
+}
+
+/* IRQs are disabled and uidhash_lock is held upon function entry.
+ * IRQ state (as stored in flags) is restored and uidhash_lock released
+ * upon function exit.
+ */
+static void free_user(struct user_struct *up, unsigned long flags)
+ __releases(&uidhash_lock)
+{
+ uid_hash_remove(up);
+ spin_unlock_irqrestore(&uidhash_lock, flags);
+ user_epoll_free(up);
+ kmem_cache_free(uid_cachep, up);
+}
+
+/*
+ * Locate the user_struct for the passed UID. If found, take a ref on it. The
+ * caller must undo that ref with free_uid().
+ *
+ * If the user_struct could not be found, return NULL.
+ */
+struct user_struct *find_user(kuid_t uid)
+{
+ struct user_struct *ret;
+ unsigned long flags;
+
+ spin_lock_irqsave(&uidhash_lock, flags);
+ ret = uid_hash_find(uid, uidhashentry(uid));
+ spin_unlock_irqrestore(&uidhash_lock, flags);
+ return ret;
+}
+
+void free_uid(struct user_struct *up)
+{
+ unsigned long flags;
+
+ if (!up)
+ return;
+
+ if (refcount_dec_and_lock_irqsave(&up->__count, &uidhash_lock, &flags))
+ free_user(up, flags);
+}
+EXPORT_SYMBOL_GPL(free_uid);
+
+struct user_struct *alloc_uid(kuid_t uid)
+{
+ struct hlist_head *hashent = uidhashentry(uid);
+ struct user_struct *up, *new;
+
+ spin_lock_irq(&uidhash_lock);
+ up = uid_hash_find(uid, hashent);
+ spin_unlock_irq(&uidhash_lock);
+
+ if (!up) {
+ new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
+ if (!new)
+ return NULL;
+
+ new->uid = uid;
+ refcount_set(&new->__count, 1);
+ if (user_epoll_alloc(new)) {
+ kmem_cache_free(uid_cachep, new);
+ return NULL;
+ }
+ ratelimit_state_init(&new->ratelimit, HZ, 100);
+ ratelimit_set_flags(&new->ratelimit, RATELIMIT_MSG_ON_RELEASE);
+
+ /*
+ * Before adding this, check whether we raced
+ * on adding the same user already..
+ */
+ spin_lock_irq(&uidhash_lock);
+ up = uid_hash_find(uid, hashent);
+ if (up) {
+ user_epoll_free(new);
+ kmem_cache_free(uid_cachep, new);
+ } else {
+ uid_hash_insert(new, hashent);
+ up = new;
+ }
+ spin_unlock_irq(&uidhash_lock);
+ }
+
+ return up;
+}
+
+static int __init uid_cache_init(void)
+{
+ int n;
+
+ uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
+ 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+
+ for(n = 0; n < UIDHASH_SZ; ++n)
+ INIT_HLIST_HEAD(uidhash_table + n);
+
+ if (user_epoll_alloc(&root_user))
+ panic("root_user epoll percpu counter alloc failed");
+
+ /* Insert the root user immediately (init already runs as root) */
+ spin_lock_irq(&uidhash_lock);
+ uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
+ spin_unlock_irq(&uidhash_lock);
+
+ return 0;
+}
+subsys_initcall(uid_cache_init);