Re: [PATCH] fs/super: fix memory leak of s_fs_info on setup_bdev_super failure

[Al Viro <viro@zeniv.linux.org.uk>]

On Fri, Nov 14, 2025 at 05:52:27PM +0100, Mehdi Ben Hadj Khelifa wrote:
> Failure in setup_bdev_super() triggers an error path where
> fc->s_fs_info ownership has already been transferred to the superblock via
> sget_fc() call in get_tree_bdev_flags() and calling put_fs_context() in
> do_new_mount() to free the s_fs_info for the specific filesystem gets
> passed in a NULL pointer.
> 
> Pass back the ownership of the s_fs_info pointer to the filesystem context
> once the error path has been triggered to be cleaned up gracefully in
> put_fs_context().
> 
> Fixes: cb50b348c71f ("convenience helpers: vfs_get_super() and sget_fc()")
> Reported-by: syzbot+ad45f827c88778ff7df6@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=ad45f827c88778ff7df6
> Signed-off-by: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@gmail.com>
> ---
> Note:This patch might need some more testing as I only did run selftests 
> with no regression, check dmesg output for no regression, run reproducer 
> with no bug.

Almost certainly bogus; quite a few fill_super() callbacks seriously count
upon "->kill_sb() will take care care of cleanup if we return an error".