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Date:   Fri, 21 Jul 2023 20:52:49 +0530
Message-Id: <87iladl25y.fsf@doe.com>
From:   Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To:     Kemeng Shi <shikemeng@huaweicloud.com>, tytso@mit.edu,
        adilger.kernel@dilger.ca, ojaswin@linux.ibm.com,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     shikemeng@huaweicloud.com
Subject: Re: [PATCH 01/10] ext4: correct grp validation in ext4_mb_good_group
In-Reply-To: <20230721171007.2065423-2-shikemeng@huaweicloud.com>
Precedence: bulk

Kemeng Shi <shikemeng@huaweicloud.com> 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@huaweicloud.com>
> ---
>  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