From: Greg Kurz <groug@kaod.org>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Vivek Goyal <vgoyal@redhat.com>,
virtio-fs@redhat.com, Greg Kurz <groug@kaod.org>,
mreitz@redhat.com, stable@vger.kernel.org
Subject: [PATCH 1/4] fuse: Fix crash in fuse_dentry_automount() error path
Date: Tue, 25 May 2021 17:02:27 +0200 [thread overview]
Message-ID: <20210525150230.157586-2-groug@kaod.org> (raw)
In-Reply-To: <20210525150230.157586-1-groug@kaod.org>
If fuse_fill_super_submount() returns an error, the error path
triggers a crash:
[ 26.206673] BUG: kernel NULL pointer dereference, address: 0000000000000000
[...]
[ 26.226362] RIP: 0010:__list_del_entry_valid+0x25/0x90
[...]
[ 26.247938] Call Trace:
[ 26.248300] fuse_mount_remove+0x2c/0x70 [fuse]
[ 26.248892] virtio_kill_sb+0x22/0x160 [virtiofs]
[ 26.249487] deactivate_locked_super+0x36/0xa0
[ 26.250077] fuse_dentry_automount+0x178/0x1a0 [fuse]
The crash happens because fuse_mount_remove() assumes that the FUSE
mount was already added to list under the FUSE connection, but this
only done after fuse_fill_super_submount() has returned success.
This means that until fuse_fill_super_submount() has returned success,
the FUSE mount isn't actually owned by the superblock. We should thus
reclaim ownership by clearing sb->s_fs_info, which will skip the call
to fuse_mount_remove(), and perform rollback, like virtio_fs_get_tree()
already does for the root sb.
Fixes: bf109c64040f ("fuse: implement crossmounts")
Cc: mreitz@redhat.com
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Greg Kurz <groug@kaod.org>
---
fs/fuse/dir.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 1b6c001a7dd1..01559061cbfb 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -339,8 +339,12 @@ static struct vfsmount *fuse_dentry_automount(struct path *path)
/* Initialize superblock, making @mp_fi its root */
err = fuse_fill_super_submount(sb, mp_fi);
- if (err)
+ if (err) {
+ fuse_conn_put(fc);
+ kfree(fm);
+ sb->s_fs_info = NULL;
goto out_put_sb;
+ }
sb->s_flags |= SB_ACTIVE;
fsc->root = dget(sb->s_root);
--
2.31.1
next prev parent reply other threads:[~2021-05-25 15:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 15:02 [PATCH 0/4] fuse: Some fixes for submounts Greg Kurz
2021-05-25 15:02 ` Greg Kurz [this message]
2021-05-27 9:51 ` [Virtio-fs] [PATCH 1/4] fuse: Fix crash in fuse_dentry_automount() error path Max Reitz
2021-05-25 15:02 ` [PATCH 2/4] fuse: Fix infinite loop in sget_fc() Greg Kurz
2021-05-27 10:08 ` [Virtio-fs] " Max Reitz
2021-05-27 12:31 ` Greg Kurz
2021-05-25 15:02 ` [PATCH 3/4] fuse: Call vfs_get_tree() for submounts Greg Kurz
2021-05-27 13:24 ` [Virtio-fs] " Max Reitz
2021-06-03 7:34 ` Greg Kurz
2021-05-25 15:02 ` [PATCH 4/4] fuse: Make fuse_fill_super_submount() static Greg Kurz
2021-05-27 13:28 ` [Virtio-fs] " Max Reitz
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210525150230.157586-2-groug@kaod.org \
--to=groug@kaod.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=mreitz@redhat.com \
--cc=stable@vger.kernel.org \
--cc=vgoyal@redhat.com \
--cc=virtio-fs@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).