Re: [PATCH] bcachefs: assign return error when iterating through layout

[Kent Overstreet]

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: syzbot+18a5c5e8a9c856944876@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=18a5c5e8a9c856944876
> Signed-off-by: Diogo Jahchan Koike <djahchankoike@xxxxxxxxx>

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
>