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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /fs/notify/dnotify/dnotify.c | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/notify/dnotify/dnotify.c')
-rw-r--r-- | fs/notify/dnotify/dnotify.c | 392 |
1 files changed, 392 insertions, 0 deletions
diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c new file mode 100644 index 000000000..e45ca6ecb --- /dev/null +++ b/fs/notify/dnotify/dnotify.c @@ -0,0 +1,392 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Directory notifications for Linux. + * + * Copyright (C) 2000,2001,2002 Stephen Rothwell + * + * Copyright (C) 2009 Eric Paris <Red Hat Inc> + * dnotify was largly rewritten to use the new fsnotify infrastructure + */ +#include <linux/fs.h> +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/sched/signal.h> +#include <linux/dnotify.h> +#include <linux/init.h> +#include <linux/security.h> +#include <linux/spinlock.h> +#include <linux/slab.h> +#include <linux/fdtable.h> +#include <linux/fsnotify_backend.h> + +int dir_notify_enable __read_mostly = 1; + +static struct kmem_cache *dnotify_struct_cache __read_mostly; +static struct kmem_cache *dnotify_mark_cache __read_mostly; +static struct fsnotify_group *dnotify_group __read_mostly; + +/* + * dnotify will attach one of these to each inode (i_fsnotify_marks) which + * is being watched by dnotify. If multiple userspace applications are watching + * the same directory with dnotify their information is chained in dn + */ +struct dnotify_mark { + struct fsnotify_mark fsn_mark; + struct dnotify_struct *dn; +}; + +/* + * When a process starts or stops watching an inode the set of events which + * dnotify cares about for that inode may change. This function runs the + * list of everything receiving dnotify events about this directory and calculates + * the set of all those events. After it updates what dnotify is interested in + * it calls the fsnotify function so it can update the set of all events relevant + * to this inode. + */ +static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark) +{ + __u32 new_mask = 0; + struct dnotify_struct *dn; + struct dnotify_mark *dn_mark = container_of(fsn_mark, + struct dnotify_mark, + fsn_mark); + + assert_spin_locked(&fsn_mark->lock); + + for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next) + new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT); + if (fsn_mark->mask == new_mask) + return; + fsn_mark->mask = new_mask; + + fsnotify_recalc_mask(fsn_mark->connector); +} + +/* + * Mains fsnotify call where events are delivered to dnotify. + * Find the dnotify mark on the relevant inode, run the list of dnotify structs + * on that mark and determine which of them has expressed interest in receiving + * events of this type. When found send the correct process and signal and + * destroy the dnotify struct if it was not registered to receive multiple + * events. + */ +static int dnotify_handle_event(struct fsnotify_mark *inode_mark, u32 mask, + struct inode *inode, struct inode *dir, + const struct qstr *name, u32 cookie) +{ + struct dnotify_mark *dn_mark; + struct dnotify_struct *dn; + struct dnotify_struct **prev; + struct fown_struct *fown; + __u32 test_mask = mask & ~FS_EVENT_ON_CHILD; + + /* not a dir, dnotify doesn't care */ + if (!dir && !(mask & FS_ISDIR)) + return 0; + + dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark); + + spin_lock(&inode_mark->lock); + prev = &dn_mark->dn; + while ((dn = *prev) != NULL) { + if ((dn->dn_mask & test_mask) == 0) { + prev = &dn->dn_next; + continue; + } + fown = &dn->dn_filp->f_owner; + send_sigio(fown, dn->dn_fd, POLL_MSG); + if (dn->dn_mask & FS_DN_MULTISHOT) + prev = &dn->dn_next; + else { + *prev = dn->dn_next; + kmem_cache_free(dnotify_struct_cache, dn); + dnotify_recalc_inode_mask(inode_mark); + } + } + + spin_unlock(&inode_mark->lock); + + return 0; +} + +static void dnotify_free_mark(struct fsnotify_mark *fsn_mark) +{ + struct dnotify_mark *dn_mark = container_of(fsn_mark, + struct dnotify_mark, + fsn_mark); + + BUG_ON(dn_mark->dn); + + kmem_cache_free(dnotify_mark_cache, dn_mark); +} + +static const struct fsnotify_ops dnotify_fsnotify_ops = { + .handle_inode_event = dnotify_handle_event, + .free_mark = dnotify_free_mark, +}; + +/* + * Called every time a file is closed. Looks first for a dnotify mark on the + * inode. If one is found run all of the ->dn structures attached to that + * mark for one relevant to this process closing the file and remove that + * dnotify_struct. If that was the last dnotify_struct also remove the + * fsnotify_mark. + */ +void dnotify_flush(struct file *filp, fl_owner_t id) +{ + struct fsnotify_mark *fsn_mark; + struct dnotify_mark *dn_mark; + struct dnotify_struct *dn; + struct dnotify_struct **prev; + struct inode *inode; + bool free = false; + + inode = file_inode(filp); + if (!S_ISDIR(inode->i_mode)) + return; + + fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group); + if (!fsn_mark) + return; + dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); + + mutex_lock(&dnotify_group->mark_mutex); + + spin_lock(&fsn_mark->lock); + prev = &dn_mark->dn; + while ((dn = *prev) != NULL) { + if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { + *prev = dn->dn_next; + kmem_cache_free(dnotify_struct_cache, dn); + dnotify_recalc_inode_mask(fsn_mark); + break; + } + prev = &dn->dn_next; + } + + spin_unlock(&fsn_mark->lock); + + /* nothing else could have found us thanks to the dnotify_groups + mark_mutex */ + if (dn_mark->dn == NULL) { + fsnotify_detach_mark(fsn_mark); + free = true; + } + + mutex_unlock(&dnotify_group->mark_mutex); + + if (free) + fsnotify_free_mark(fsn_mark); + fsnotify_put_mark(fsn_mark); +} + +/* this conversion is done only at watch creation */ +static __u32 convert_arg(unsigned long arg) +{ + __u32 new_mask = FS_EVENT_ON_CHILD; + + if (arg & DN_MULTISHOT) + new_mask |= FS_DN_MULTISHOT; + if (arg & DN_DELETE) + new_mask |= (FS_DELETE | FS_MOVED_FROM); + if (arg & DN_MODIFY) + new_mask |= FS_MODIFY; + if (arg & DN_ACCESS) + new_mask |= FS_ACCESS; + if (arg & DN_ATTRIB) + new_mask |= FS_ATTRIB; + if (arg & DN_RENAME) + new_mask |= FS_DN_RENAME; + if (arg & DN_CREATE) + new_mask |= (FS_CREATE | FS_MOVED_TO); + + return new_mask; +} + +/* + * If multiple processes watch the same inode with dnotify there is only one + * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct + * onto that mark. This function either attaches the new dnotify_struct onto + * that list, or it |= the mask onto an existing dnofiy_struct. + */ +static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark, + fl_owner_t id, int fd, struct file *filp, __u32 mask) +{ + struct dnotify_struct *odn; + + odn = dn_mark->dn; + while (odn != NULL) { + /* adding more events to existing dnofiy_struct? */ + if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { + odn->dn_fd = fd; + odn->dn_mask |= mask; + return -EEXIST; + } + odn = odn->dn_next; + } + + dn->dn_mask = mask; + dn->dn_fd = fd; + dn->dn_filp = filp; + dn->dn_owner = id; + dn->dn_next = dn_mark->dn; + dn_mark->dn = dn; + + return 0; +} + +/* + * When a process calls fcntl to attach a dnotify watch to a directory it ends + * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be + * attached to the fsnotify_mark. + */ +int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) +{ + struct dnotify_mark *new_dn_mark, *dn_mark; + struct fsnotify_mark *new_fsn_mark, *fsn_mark; + struct dnotify_struct *dn; + struct inode *inode; + fl_owner_t id = current->files; + struct file *f; + int destroy = 0, error = 0; + __u32 mask; + + /* we use these to tell if we need to kfree */ + new_fsn_mark = NULL; + dn = NULL; + + if (!dir_notify_enable) { + error = -EINVAL; + goto out_err; + } + + /* a 0 mask means we are explicitly removing the watch */ + if ((arg & ~DN_MULTISHOT) == 0) { + dnotify_flush(filp, id); + error = 0; + goto out_err; + } + + /* dnotify only works on directories */ + inode = file_inode(filp); + if (!S_ISDIR(inode->i_mode)) { + error = -ENOTDIR; + goto out_err; + } + + /* + * convert the userspace DN_* "arg" to the internal FS_* + * defined in fsnotify + */ + mask = convert_arg(arg); + + error = security_path_notify(&filp->f_path, mask, + FSNOTIFY_OBJ_TYPE_INODE); + if (error) + goto out_err; + + /* expect most fcntl to add new rather than augment old */ + dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL); + if (!dn) { + error = -ENOMEM; + goto out_err; + } + + /* new fsnotify mark, we expect most fcntl calls to add a new mark */ + new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL); + if (!new_dn_mark) { + error = -ENOMEM; + goto out_err; + } + + /* set up the new_fsn_mark and new_dn_mark */ + new_fsn_mark = &new_dn_mark->fsn_mark; + fsnotify_init_mark(new_fsn_mark, dnotify_group); + new_fsn_mark->mask = mask; + new_dn_mark->dn = NULL; + + /* this is needed to prevent the fcntl/close race described below */ + mutex_lock(&dnotify_group->mark_mutex); + + /* add the new_fsn_mark or find an old one. */ + fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group); + if (fsn_mark) { + dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); + spin_lock(&fsn_mark->lock); + } else { + error = fsnotify_add_inode_mark_locked(new_fsn_mark, inode, 0); + if (error) { + mutex_unlock(&dnotify_group->mark_mutex); + goto out_err; + } + spin_lock(&new_fsn_mark->lock); + fsn_mark = new_fsn_mark; + dn_mark = new_dn_mark; + /* we used new_fsn_mark, so don't free it */ + new_fsn_mark = NULL; + } + + rcu_read_lock(); + f = fcheck(fd); + rcu_read_unlock(); + + /* if (f != filp) means that we lost a race and another task/thread + * actually closed the fd we are still playing with before we grabbed + * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the + * fd is the only time we clean up the marks we need to get our mark + * off the list. */ + if (f != filp) { + /* if we added ourselves, shoot ourselves, it's possible that + * the flush actually did shoot this fsn_mark. That's fine too + * since multiple calls to destroy_mark is perfectly safe, if + * we found a dn_mark already attached to the inode, just sod + * off silently as the flush at close time dealt with it. + */ + if (dn_mark == new_dn_mark) + destroy = 1; + error = 0; + goto out; + } + + __f_setown(filp, task_pid(current), PIDTYPE_TGID, 0); + + error = attach_dn(dn, dn_mark, id, fd, filp, mask); + /* !error means that we attached the dn to the dn_mark, so don't free it */ + if (!error) + dn = NULL; + /* -EEXIST means that we didn't add this new dn and used an old one. + * that isn't an error (and the unused dn should be freed) */ + else if (error == -EEXIST) + error = 0; + + dnotify_recalc_inode_mask(fsn_mark); +out: + spin_unlock(&fsn_mark->lock); + + if (destroy) + fsnotify_detach_mark(fsn_mark); + mutex_unlock(&dnotify_group->mark_mutex); + if (destroy) + fsnotify_free_mark(fsn_mark); + fsnotify_put_mark(fsn_mark); +out_err: + if (new_fsn_mark) + fsnotify_put_mark(new_fsn_mark); + if (dn) + kmem_cache_free(dnotify_struct_cache, dn); + return error; +} + +static int __init dnotify_init(void) +{ + dnotify_struct_cache = KMEM_CACHE(dnotify_struct, + SLAB_PANIC|SLAB_ACCOUNT); + dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC|SLAB_ACCOUNT); + + dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops); + if (IS_ERR(dnotify_group)) + panic("unable to allocate fsnotify group for dnotify\n"); + return 0; +} + +module_init(dnotify_init) |