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fanotify: disallow mount/sb marks on kernel internal pseudo fs

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Hopefully, nobody is trying to abuse mount/sb marks for watching all
anonymous pipes/inodes.

I cannot think of a good reason to allow this - it looks like an
oversight that dated back to the original fanotify API.

Link: https://lore.kernel.org/linux-fsdevel/20230628101132.kvchg544mczxv2pm@quack3/
Fixes: 0ff21db9fc ("fanotify: hooks the fanotify_mark syscall to the vfsmount code")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230629042044.25723-1-amir73il@gmail.com>
This commit is contained in:
Amir Goldstein 2023-06-29 07:20:44 +03:00 committed by Jan Kara
parent a901a3568f
commit 69562eb0bd
1 changed files with 14 additions and 0 deletions
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14
fs/notify/fanotify/fanotify_user.c
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@ -1622,6 +1622,20 @@ static int fanotify_events_supported(struct fsnotify_group *group,
path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
return -EINVAL;
/*
* mount and sb marks are not allowed on kernel internal pseudo fs,
* like pipe_mnt, because that would subscribe to events on all the
* anonynous pipes in the system.
*
* SB_NOUSER covers all of the internal pseudo fs whose objects are not
* exposed to user's mount namespace, but there are other SB_KERNMOUNT
* fs, like nsfs, debugfs, for which the value of allowing sb and mount
* mark is questionable. For now we leave them alone.
*/
if (mark_type != FAN_MARK_INODE &&
path->mnt->mnt_sb->s_flags & SB_NOUSER)
return -EINVAL;
/*
* We shouldn't have allowed setting dirent events and the directory
* flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,