linux-kernel - Re: [PATCH 6/7] ext4: set type of ac_groups_linear_remaining to _

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Message-ID: <fad39d52-1d82-27ed-b074-f002a9cc2d48@huawei.com>
Date: Sat, 27 Jan 2024 10:10:55 +0800
From: Zhang Yi <yi.zhang@...wei.com>
To: Baokun Li <libaokun1@...wei.com>, <linux-ext4@...r.kernel.org>
CC: <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>,
	<ritesh.list@...il.com>, <linux-kernel@...r.kernel.org>,
	<yangerkun@...wei.com>, <chengzhihao1@...wei.com>, <yukuai3@...wei.com>,
	<stable@...nel.org>
Subject: Re: [PATCH 6/7] ext4: set type of ac_groups_linear_remaining to __u32
 to avoid overflow

On 2024/1/26 16:57, Baokun Li wrote:
> Now ac_groups_linear_remaining is of type __u16 and s_mb_max_linear_groups
> is of type unsigned int, so an overflow occurs when setting a value above
> 65535 through the mb_max_linear_groups sysfs interface. Therefore, the
> type of ac_groups_linear_remaining is set to __u32 to avoid overflow.
> 
> Fixes: 196e402adf2e ("ext4: improve cr 0 / cr 1 group scanning")
> CC: stable@...nel.org
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

Looks good to me.

Reviewed-by: Zhang Yi <yi.zhang@...wei.com>

> ---
>  fs/ext4/mballoc.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
> index d7aeb5da7d86..498af2abc5d8 100644
> --- a/fs/ext4/mballoc.h
> +++ b/fs/ext4/mballoc.h
> @@ -194,8 +194,8 @@ struct ext4_allocation_context {
>  
>  	__u32 ac_groups_considered;
>  	__u32 ac_flags;		/* allocation hints */
> +	__u32 ac_groups_linear_remaining;
>  	__u16 ac_groups_scanned;
> -	__u16 ac_groups_linear_remaining;
>  	__u16 ac_found;
>  	__u16 ac_cX_found[EXT4_MB_NUM_CRS];
>  	__u16 ac_tail;
>