From: Amir Goldstein amir73il@gmail.com
[ Upstream commit ceaf69f8eadcafb323392be88e7a5248c415d423 ]
Dirent events (create/delete/move) are only reported on watched directory inodes, but in fanotify as well as in legacy inotify, it was always allowed to set them on non-dir inode, which does not result in any meaningful outcome.
Until kernel v5.17, dirent events in fanotify also differed from events "on child" (e.g. FAN_OPEN) in the information provided in the event. For example, FAN_OPEN could be set in the mask of a non-dir or the mask of its parent and event would report the fid of the child regardless of the marked object. By contrast, FAN_DELETE is not reported if the child is marked and the child fid was not reported in the events.
Since kernel v5.17, with fanotify group flag FAN_REPORT_TARGET_FID, the fid of the child is reported with dirent events, like events "on child", which may create confusion for users expecting the same behavior as events "on child" when setting events in the mask on a child.
The desired semantics of setting dirent events in the mask of a child are not clear, so for now, deny this action for a group initialized with flag FAN_REPORT_TARGET_FID and for the new event FAN_RENAME. We may relax this restriction in the future if we decide on the semantics and implement them.
Fixes: d61fd650e9d2 ("fanotify: introduce group flag FAN_REPORT_TARGET_FID") Fixes: 8cc3b1ccd930 ("fanotify: wire up FAN_RENAME event") Link: https://lore.kernel.org/linux-fsdevel/20220505133057.zm5t6vumc4xdcnsg@quack3... Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Jan Kara jack@suse.cz Link: https://lore.kernel.org/r/20220507080028.219826-1-amir73il@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/notify/fanotify/fanotify_user.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 2ff6bd85ba8f..f2a1947ec5ee 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -1638,6 +1638,19 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, else mnt = path.mnt;
+ /* + * FAN_RENAME is not allowed on non-dir (for now). + * We shouldn't have allowed setting any dirent events in mask of + * non-dir, but because we always allowed it, error only if group + * was initialized with the new flag FAN_REPORT_TARGET_FID. + */ + ret = -ENOTDIR; + if (inode && !S_ISDIR(inode->i_mode) && + ((mask & FAN_RENAME) || + ((mask & FANOTIFY_DIRENT_EVENTS) && + FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID)))) + goto path_put_and_out; + /* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */ if (mnt || !S_ISDIR(inode->i_mode)) { mask &= ~FAN_EVENT_ON_CHILD;