linux-kernel - Re: [PATCH] btrfs: Refactor allocation size calculation in kzalloc()

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Message-ID: <342929a3-ac5f-4953-a763-b81c60e66554@gmail.com>
Date: Tue, 30 Sep 2025 10:27:06 +0100
From: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@...il.com>
To: Qu Wenruo <quwenruo.btrfs@....com>, clm@...com, dsterba@...e.com
Cc: linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 skhan@...uxfoundation.org, david.hunter.linux@...il.com,
 linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] btrfs: Refactor allocation size calculation in kzalloc()

On 9/30/25 10:19 AM, Qu Wenruo wrote:
> 
> 
> 在 2025/9/30 18:44, Mehdi Ben Hadj Khelifa 写道:
>> Wrap allocation size calculation in size_add() and size_mul() to avoid
>> any potential overflow.
>>
>> Signed-off-by: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@...il.com>
>> ---
>>   fs/btrfs/volumes.c | 11 +++++------
>>   1 file changed, 5 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index c6e3efd6f602..3f1f19b28aac 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -6076,12 +6076,11 @@ struct btrfs_io_context 
>> *alloc_btrfs_io_context(struct btrfs_fs_info *fs_info,
>>   {
>>       struct btrfs_io_context *bioc;
>> -    bioc = kzalloc(
>> -         /* The size of btrfs_io_context */
>> -        sizeof(struct btrfs_io_context) +
>> -        /* Plus the variable array for the stripes */
>> -        sizeof(struct btrfs_io_stripe) * (total_stripes),
>> -        GFP_NOFS);
>> +    /* The size of btrfs_io_context */
>> +    /* Plus the variable array for the stripes */
>> +    bioc = kzalloc(size_add(sizeof(struct btrfs_io_context),
> 
> Please use struct_size() instead.
> 
> And if you're using struct_size() there iwll be no need for any comments.

Understood, I will get v2 on the way with your recommendation.
Thank you for the suggestion.
Regards,
Mehdi

>> +                size_mul(sizeof(struct btrfs_io_stripe),
>> +                        total_stripes)), GFP_NOFS);
>>       if (!bioc)
>>           return NULL;
>