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| author |   Greg Kurz <groug@kaod.org> | 2021-06-04 18:11:50 +0200 |
|---|---|---|
| committer |   Miklos Szeredi <mszeredi@redhat.com> | 2021-06-09 15:33:40 +0200 |
| commit | d92d88f0568e97c437eeb79d9c9609bd8277406f (patch) | |
| tree | e7a4a14017bdd9fcd175b3bb27a560011c8180f5 /fs/fuse/dir.c | |
| parent | Linux 5.13-rc5 (diff) | |
| download | linux-dev-d92d88f0568e97c437eeb79d9c9609bd8277406f.tar.xz linux-dev-d92d88f0568e97c437eeb79d9c9609bd8277406f.zip | |
fuse: Fix crash in fuse_dentry_automount() error path
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: stable@vger.kernel.org # v5.10+
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/fuse/dir.c')
| -rw-r--r-- | fs/fuse/dir.c | 6 |
1 files changed, 5 insertions, 1 deletions
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); |