On Mon, Sep 23, 2024 at 07:22:14PM GMT, Diogo Jahchan Koike wrote:
> syzbot reported a null ptr deref in __copy_user [0]
>
> In __bch2_read_super, when a corrupt backup superblock matches the
> default opts offset, no error is assigned to ret and the freed superblock
> gets through, possibly being assigned as the best sb in bch2_fs_open and
> being later dereferenced, causing a fault. Assign EINVALID to ret when
> iterating through layout.
>
> [0]: https://syzkaller.appspot.com/bug?extid=18a5c5e8a9c856944876
>
> Reported-by: [email protected]
> Closes: https://syzkaller.appspot.com/bug?extid=18a5c5e8a9c856944876
> Signed-off-by: Diogo Jahchan Koike <[email protected]>
Thanks, applied
> ---
> fs/bcachefs/super-io.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
> index c8c2ccbdfbb5..fbca0bd302db 100644
> --- a/fs/bcachefs/super-io.c
> +++ b/fs/bcachefs/super-io.c
> @@ -796,8 +796,10 @@ static int __bch2_read_super(const char *path, struct
> bch_opts *opts,
> i < layout.sb_offset + layout.nr_superblocks; i++) {
> offset = le64_to_cpu(*i);
>
> - if (offset == opt_get(*opts, sb))
> + if (offset == opt_get(*opts, sb)) {
> + ret = -BCH_ERR_invalid;
> continue;
> + }
>
> ret = read_one_super(sb, offset, &err);
> if (!ret)
> --
> 2.43.0
>
