block: reject block device inodes with i_rdev == 0 in lookup_bdev()

lookup_bdev() blindly returns inode->i_rdev without validating it.
When a FUSE filesystem exposes a root inode with S_IFBLK mode but
i_rdev == 0 (via rootmode=060000), any subsequent mount attempt using
that path as a block device source propagates dev_t 0 into the
superblock machinery.  After commit 9ee5f161a4db ("fs: maintain a
global device-to-superblock table") this triggers a WARNING in
super_dev_register().

Reject i_rdev == 0 early with -ENODEV since no real block device
driver registers major 0.

Reported-by: syzbot+72fe3ea5814121fbc76e@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=72fe3ea5814121fbc76e
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Link: https://patch.msgid.link/20260703065548.1135125-1-yun.zhou@windriver.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions