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fanotify: disallow mount/sb marks on kernel internal pseudo fs
commit69562eb0bd
upstream. 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> [backport to 5.x.y] Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 20 additions and 2 deletions
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@ -928,8 +928,11 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
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return 0;
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return 0;
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}
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}
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static int fanotify_events_supported(struct path *path, __u64 mask)
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static int fanotify_events_supported(struct path *path, __u64 mask,
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unsigned int flags)
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{
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{
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unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
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/*
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/*
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* Some filesystems such as 'proc' acquire unusual locks when opening
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* Some filesystems such as 'proc' acquire unusual locks when opening
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* files. For them fanotify permission events have high chances of
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* files. For them fanotify permission events have high chances of
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@ -941,6 +944,21 @@ static int fanotify_events_supported(struct path *path, __u64 mask)
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if (mask & FANOTIFY_PERM_EVENTS &&
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if (mask & FANOTIFY_PERM_EVENTS &&
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path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
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path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
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return -EINVAL;
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return -EINVAL;
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/*
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* mount and sb marks are not allowed on kernel internal pseudo fs,
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* like pipe_mnt, because that would subscribe to events on all the
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* anonynous pipes in the system.
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*
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* SB_NOUSER covers all of the internal pseudo fs whose objects are not
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* exposed to user's mount namespace, but there are other SB_KERNMOUNT
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* fs, like nsfs, debugfs, for which the value of allowing sb and mount
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* mark is questionable. For now we leave them alone.
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*/
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if (mark_type != FAN_MARK_INODE &&
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path->mnt->mnt_sb->s_flags & SB_NOUSER)
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return -EINVAL;
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return 0;
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return 0;
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}
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}
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@ -1050,7 +1068,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
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goto fput_and_out;
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goto fput_and_out;
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if (flags & FAN_MARK_ADD) {
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if (flags & FAN_MARK_ADD) {
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ret = fanotify_events_supported(&path, mask);
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ret = fanotify_events_supported(&path, mask, flags);
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if (ret)
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if (ret)
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goto path_put_and_out;
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goto path_put_and_out;
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}
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}
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