This is a note to let you know that I've just added the patch titled
fanotify: disallow mount/sb marks on kernel internal pseudo fs
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fanotify-disallow-mount-sb-marks-on-kernel-internal-pseudo-fs.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 69562eb0bd3e6bb8e522a7b254334e0fb30dff0c Mon Sep 17 00:00:00 2001
From: Amir Goldstein <amir73il@xxxxxxxxx>
Date: Thu, 29 Jun 2023 07:20:44 +0300
Subject: fanotify: disallow mount/sb marks on kernel internal pseudo fs
From: Amir Goldstein <amir73il@xxxxxxxxx>
commit 69562eb0bd3e6bb8e522a7b254334e0fb30dff0c 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: 0ff21db9fcc3 ("fanotify: hooks the fanotify_mark syscall to the vfsmount code")
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Message-Id: <20230629042044.25723-1-amir73il@xxxxxxxxx>
[backport to 5.x.y]
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/notify/fanotify/fanotify_user.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1337,8 +1337,11 @@ static int fanotify_test_fid(struct path
return 0;
}
-static int fanotify_events_supported(struct path *path, __u64 mask)
+static int fanotify_events_supported(struct path *path, __u64 mask,
+ unsigned int flags)
{
+ unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
+
/*
* Some filesystems such as 'proc' acquire unusual locks when opening
* files. For them fanotify permission events have high chances of
@@ -1350,6 +1353,21 @@ static int fanotify_events_supported(str
if (mask & FANOTIFY_PERM_EVENTS &&
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;
+
return 0;
}
@@ -1476,7 +1494,7 @@ static int do_fanotify_mark(int fanotify
goto fput_and_out;
if (flags & FAN_MARK_ADD) {
- ret = fanotify_events_supported(&path, mask);
+ ret = fanotify_events_supported(&path, mask, flags);
if (ret)
goto path_put_and_out;
}
Patches currently in stable-queue which might be from amir73il@xxxxxxxxx are
queue-5.15/ovl-update-of-dentry-revalidate-flags-after-copy-up.patch
queue-5.15/ovl-fix-null-pointer-dereference-in-ovl_get_acl_rcu.patch
queue-5.15/fanotify-disallow-mount-sb-marks-on-kernel-internal-pseudo-fs.patch
