kernel.git/fs/notify/mark.c, branch linux-4.19.y

fsnotify: fix wrong lockdep annotations

2022-06-14T14:59:20Z

[ Upstream commit 623af4f538b5df9b416e1b82f720af7371b4c771 ] Commit 6960b0d909cd ("fsnotify: change locking order") changed some of the mark_mutex locks in direct reclaim path to use: mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING); This change is explained: "...It uses nested locking to avoid deadlock in case we do the final iput() on an inode which still holds marks and thus would take the mutex again when calling fsnotify_inode_delete() in destroy_inode()." The problem is that the mutex_lock_nested() is not a nested lock at all. In fact, it has the opposite effect of preventing lockdep from warning about a very possible deadlock. Due to these wrong annotations, a deadlock that was introduced with nfsd filecache in kernel v5.4 went unnoticed in v5.4.y for over two years until it was reported recently by Khazhismel Kumykov, only to find out that the deadlock was already fixed in kernel v5.5. Fix the wrong lockdep annotations. Cc: Khazhismel Kumykov Fixes: 6960b0d909cd ("fsnotify: change locking order") Link: https://lore.kernel.org/r/20220321112310.vpr7oxro2xkz5llh@quack3.lan/ Link: https://lore.kernel.org/r/20220422120327.3459282-4-amir73il@gmail.com Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

fsnotify: Fix busy inodes during unmount

2018-11-13T19:08:50Z

commit 721fb6fbfd2132164c2e8777cc837f9b2c1794dc upstream. Detaching of mark connector from fsnotify_put_mark() can race with unmounting of the filesystem like: CPU1 CPU2 fsnotify_put_mark() spin_lock(&conn->lock); ... inode = fsnotify_detach_connector_from_object(conn) spin_unlock(&conn->lock); generic_shutdown_super() fsnotify_unmount_inodes() sees connector detached for inode -> nothing to do evict_inode() barfs on pending inode reference iput(inode); Resulting in "Busy inodes after unmount" message and possible kernel oops. Make fsnotify_unmount_inodes() properly wait for outstanding inode references from detached connectors. Note that the accounting of outstanding inode references in the superblock can cause some cacheline contention on the counter. OTOH it happens only during deletion of the last notification mark from an inode (or during unlinking of watched inode) and that is not too bad. I have measured time to create & delete inotify watch 100000 times from 64 processes in parallel (each process having its own inotify group and its own file on a shared superblock) on a 64 CPU machine. Average and standard deviation of 15 runs look like: Avg Stddev Vanilla 9.817400 0.276165 Fixed 9.710467 0.228294 So there's no statistically significant difference. Fixes: 6b3f05d24d35 ("fsnotify: Detach mark from object list when last reference is dropped") CC: stable@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

fsnotify: fix false positive warning on inode delete

2018-08-20T11:55:45Z

When inode is getting deleted and someone else holds reference to a mark attached to the inode, we just detach the connector from the inode. In that case fsnotify_put_mark() called from fsnotify_destroy_marks() will decide to recalculate mask for the inode and __fsnotify_recalc_mask() will WARN about invalid connector type: WARNING: CPU: 1 PID: 12015 at fs/notify/mark.c:139 __fsnotify_recalc_mask+0x2d7/0x350 fs/notify/mark.c:139 Actually there's no reason to warn about detached connector in __fsnotify_recalc_mask() so just silently skip updating the mask in such case. Reported-by: syzbot+c34692a51b9a6ca93540@syzkaller.appspotmail.com Fixes: 3ac70bfcde81 ("fsnotify: add helper to get mask from connector") Signed-off-by: Jan Kara

fsnotify: add helper to get mask from connector

2018-06-27T11:45:07Z

Use a helper to get the mask from the object (i.e. i_fsnotify_mask) to generalize code of add/remove inode/vfsmount mark. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara

fsnotify: let connector point to an abstract object

2018-06-27T11:45:05Z

Make the code to attach/detach a connector to object more generic by letting the fsnotify connector point to an abstract fsnotify_connp_t. Code that needs to dereference an inode or mount object now uses the helpers fsnotify_conn_{inode,mount}. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara

fsnotify: pass connp and object type to fsnotify_add_mark()

2018-06-27T11:45:03Z

Instead of passing inode and vfsmount arguments to fsnotify_add_mark() and its _locked variant, pass an abstract object pointer and the object type. The helpers fsnotify_obj_{inode,mount} are added to get the concrete object pointer from abstract object pointer. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara

fsnotify: use typedef fsnotify_connp_t for brevity

2018-06-27T11:44:59Z

The object marks manipulation functions fsnotify_destroy_marks() fsnotify_find_mark() and their helpers take an argument of type struct fsnotify_mark_connector __rcu ** to dereference the connector pointer. use a typedef to describe this type for brevity. Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara

fsnotify: generalize iteration of marks by object type

2018-05-18T12:58:22Z

Make some code that handles marks of object types inode and vfsmount generic, so it can handle other object types. Introduce fsnotify_foreach_obj_type macro to iterate marks by object type and fsnotify_iter_{should|set}_report_type macros to set/test report_mask. This is going to be used for adding mark of another object type (super block mark). Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara

fsnotify: use type id to identify connector object type

2018-05-18T12:58:22Z

An fsnotify_mark_connector is referencing a single type of object (either inode or vfsmount). Instead of storing a type mask in connector->flags, store a single type id in connector->type to identify the type of object. When a connector object is detached from the object, its type is set to FSNOTIFY_OBJ_TYPE_DETACHED and this object is not going to be reused. The function fsnotify_clear_marks_by_group() is the only place where type mask was used, so use type flags instead of type id to this function. This change is going to be more convenient when adding a new object type (super block). Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara

fsnotify: convert fsnotify_mark.refcnt from atomic_t to refcount_t

2017-10-31T16:54:56Z

atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable fsnotify_mark.refcnt is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Jan Kara