| Message ID | 20210604161156.408496-3-groug@kaod.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fuse: Some fixes for submounts | expand |
On 04.06.21 18:11, Greg Kurz wrote: > As soon as fuse_dentry_automount() does up_write(&sb->s_umount), the > superblock can theoretically be killed. If this happens before the > submount was added to the &fc->mounts list, fuse_mount_remove() later > crashes in list_del_init() because it assumes the submount to be > already there. > > Add the submount before dropping sb->s_umount to fix the inconsistency. > It is okay to nest fc->killsb under sb->s_umount, we already do this > on the ->kill_sb() path. > > Signed-off-by: Greg Kurz <groug@kaod.org> > --- > fs/fuse/dir.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) Reviewed-by: Max Reitz <mreitz@redhat.com>
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 01559061cbfb..3fd1b71e546b 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -346,15 +346,15 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) goto out_put_sb; } + down_write(&fc->killsb); + list_add_tail(&fm->fc_entry, &fc->mounts); + up_write(&fc->killsb); + sb->s_flags |= SB_ACTIVE; fsc->root = dget(sb->s_root); /* We are done configuring the superblock, so unlock it */ up_write(&sb->s_umount); - down_write(&fc->killsb); - list_add_tail(&fm->fc_entry, &fc->mounts); - up_write(&fc->killsb); - /* Create the submount */ mnt = vfs_create_mount(fsc); if (IS_ERR(mnt)) {
As soon as fuse_dentry_automount() does up_write(&sb->s_umount), the superblock can theoretically be killed. If this happens before the submount was added to the &fc->mounts list, fuse_mount_remove() later crashes in list_del_init() because it assumes the submount to be already there. Add the submount before dropping sb->s_umount to fix the inconsistency. It is okay to nest fc->killsb under sb->s_umount, we already do this on the ->kill_sb() path. Signed-off-by: Greg Kurz <groug@kaod.org> --- fs/fuse/dir.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)