Re: [PATCH 01/10] ext4: correct grp validation in ext4_mb_good_group

[IBM]

Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx> writes:

> Group corruption check will access memory of grp and will trigger kernel
> crash if grp is NULL. So do NULL check before corruption check.
>

Fixes: 5354b2af3406 ("ext4: allow ext4_get_group_info() to fail")

> Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
> ---
>  fs/ext4/mballoc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 3ab37533349f..90ffabac100b 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2554,7 +2554,7 @@ static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
>  
>  	BUG_ON(cr < CR_POWER2_ALIGNED || cr >= EXT4_MB_NUM_CRS);
>  
> -	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp) || !grp))
> +	if (!grp || unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))

maybe like below?
      if (unlikely(!grp || EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))

-ritesh

>  		return false;
>  
>  	free = grp->bb_free;
> -- 
> 2.30.0