kernel/linux.git/fs/notify/mark.c, branch v6.12.80

fsnotify: Fix ordering of iput() and watched_objects decrement

2024-12-05T13:02:46+00:00

commit 21d1b618b6b9da46c5116c640ac4b1cc8d40d63a upstream. Ensure the superblock is kept alive until we're done with iput(). Holding a reference to an inode is not allowed unless we ensure the superblock stays alive, which fsnotify does by keeping the watched_objects count elevated, so iput() must happen before the watched_objects decrement. This can lead to a UAF of something like sb->s_fs_info in tmpfs, but the UAF is hard to hit because race orderings that oops are more likely, thanks to the CHECK_DATA_CORRUPTION() block in generic_shutdown_super(). Also, ensure that fsnotify_put_sb_watched_objects() doesn't call fsnotify_sb_watched_objects() on a superblock that may have already been freed, which would cause a UAF read of sb->s_fsnotify_info. Cc: stable@kernel.org Fixes: d2f277e26f52 ("fsnotify: rename fsnotify_{get,put}_sb_connectors()") Signed-off-by: Jann Horn Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

fsnotify: Avoid data race between fsnotify_recalc_mask() and fsnotify_object_watched()

2024-10-02T13:11:40+00:00

When __fsnotify_recalc_mask() recomputes the mask on the watched object, the compiler can "optimize" the code to perform partial updates to the mask (including zeroing it at the beginning). Thus places checking the object mask without conn->lock such as fsnotify_object_watched() could see invalid states of the mask. Make sure the mask update is performed by one memory store using WRITE_ONCE(). Reported-by: syzbot+701037856c25b143f1ad@syzkaller.appspotmail.com Reported-by: Dmitry Vyukov Link: https://lore.kernel.org/all/CACT4Y+Zk0ohwwwHSD63U2-PQ=UuamXczr1mKBD6xtj2dyYKBvA@mail.gmail.com Signed-off-by: Jan Kara Reviewed-by: Josef Bacik Link: https://patch.msgid.link/20240717140623.27768-1-jack@suse.cz

fsnotify: clear PARENT_WATCHED flags lazily

2024-06-05T07:52:38+00:00

In some setups directories can have many (usually negative) dentries. Hence __fsnotify_update_child_dentry_flags() function can take a significant amount of time. Since the bulk of this function happens under inode->i_lock this causes a significant contention on the lock when we remove the watch from the directory as the __fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask() races with __fsnotify_update_child_dentry_flags() calls from __fsnotify_parent() happening on children. This can lead upto softlockup reports reported by users. Fix the problem by calling fsnotify_update_children_dentry_flags() to set PARENT_WATCHED flags only when parent starts watching children. When parent stops watching children, clear false positive PARENT_WATCHED flags lazily in __fsnotify_parent() for each accessed child. Suggested-by: Jan Kara Signed-off-by: Amir Goldstein Signed-off-by: Stephen Brennan Signed-off-by: Jan Kara

fsnotify: optimize the case of no permission event watchers

2024-04-04T14:24:16+00:00

Commit e43de7f0862b ("fsnotify: optimize the case of no marks of any type") optimized the case where there are no fsnotify watchers on any of the filesystem's objects. It is quite common for a system to have a single local filesystem and it is quite common for the system to have some inotify watches on some config files or directories, so the optimization of no marks at all is often not in effect. Permission event watchers, which require high priority group are more rare, so optimizing the case of no marks og high priority groups can improve performance for more systems, especially for performance sensitive io workloads. Count per-sb watched objects by high priority groups and use that the optimize out the call to __fsnotify_parent() and fsnotify() in fsnotify permission hooks. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20240317184154.1200192-11-amir73il@gmail.com>

fsnotify: lazy attach fsnotify_sb_info state to sb

2024-04-04T14:24:16+00:00

Define a container struct fsnotify_sb_info to hold per-sb state, including the reference to sb marks connector. Allocate the fsnotify_sb_info state before attaching connector to any object on the sb and free it only when killing sb. This state is going to be used for storing per priority watched objects counters. Suggested-by: Jan Kara Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20240317184154.1200192-8-amir73il@gmail.com>

fsnotify: create helper fsnotify_update_sb_watchers()

2024-04-04T14:24:16+00:00

We would like to count watched objects by priority group, so we will need to update the watched object counter after adding/removing marks. Create a helper fsnotify_update_sb_watchers() and call it after attaching/detaching a mark, instead of fsnotify_{get,put}_sb_watchers() only after attaching/detaching a connector. Soon, we will use this helper to count watched objects by the highest watching priority group. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20240317184154.1200192-7-amir73il@gmail.com>

fsnotify: pass object pointer and type to fsnotify mark helpers

2024-04-04T14:24:16+00:00

Instead of passing fsnotify_connp_t, pass the pointer to the marked object. Store the object pointer in the connector and move the definition of fsnotify_connp_t to internal fsnotify subsystem API, so it is no longer used by fsnotify backends. Suggested-by: Jan Kara Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20240317184154.1200192-6-amir73il@gmail.com>

fsnotify: create helpers to get sb and connp from object

2024-04-04T14:23:46+00:00

In preparation to passing an object pointer to add/remove/find mark helpers, create helpers to get sb and connp by object type. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20240317184154.1200192-3-amir73il@gmail.com>

fsnotify: rename fsnotify_{get,put}_sb_connectors()

2024-04-04T14:21:12+00:00

Instead of counting the number of connectors in an sb, we would like to count the number of watched objects per priority group. As a start, create an accessor fsnotify_sb_watched_objects() to s_fsnotify_connectors and rename the fsnotify_{get,put}_sb_connectors() helpers to fsnotify_{get,put}_sb_watchers() to better describes the counter. Increment the counter at the end of fsnotify_attach_connector_to_object() if connector was attached instead of decrementing it on race to connect. This is fine, because fsnotify_delete_sb() cannot be running in parallel to fsnotify_attach_connector_to_object() which requires a reference to a filesystem object. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20240317184154.1200192-2-amir73il@gmail.com>

fanotify: store fsid in mark instead of in connector

2023-12-01T09:55:21+00:00

Some filesystems like fuse and nfs have zero or non-unique fsid. We would like to avoid reporting ambiguous fsid in events, so we need to avoid marking objects with same fsid and different sb. To make this easier to enforce, store the fsid in the marks of the group instead of in the shared conenctor. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20231130165619.3386452-2-amir73il@gmail.com>