linux-kernel - Re: [PATCH v2] ksmbd: prevent memory leak on error return

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Message-ID: <b503d929-ff3a-4dc3-9de8-aa0eb00d181a@gmail.com>
Date:   Sun, 19 Nov 2023 01:14:06 -0800
From:   Pierre Mariani <pierre.mariani@...il.com>
To:     Zongmin Zhou <min_halo@....com>, linkinjeon@...nel.org
Cc:     linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org,
        senozhatsky@...omium.org, sfrench@...ba.org, tom@...pey.com,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <error27@...il.com>,
        Zongmin Zhou <zhouzongmin@...inos.cn>
Subject: Re: [PATCH v2] ksmbd: prevent memory leak on error return

On 11/8/2023 5:17 PM, Zongmin Zhou wrote:
> When allocated memory for 'new' failed,just return
> will cause memory leak of 'ar'.
> 
> v2: rollback iov_alloc_cnt when allocate memory failed.
> 
> Fixes: 1819a9042999 ("ksmbd: reorganize ksmbd_iov_pin_rsp()")
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <error27@...il.com>
> Closes: https://lore.kernel.org/r/202311031837.H3yo7JVl-lkp@intel.com/
> Signed-off-by: Zongmin Zhou<zhouzongmin@...inos.cn>
> ---
>  fs/smb/server/ksmbd_work.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/smb/server/ksmbd_work.c b/fs/smb/server/ksmbd_work.c
> index a2ed441e837a..44bce4c56daf 100644
> --- a/fs/smb/server/ksmbd_work.c
> +++ b/fs/smb/server/ksmbd_work.c
> @@ -123,8 +123,11 @@ static int __ksmbd_iov_pin_rsp(struct ksmbd_work *work, void *ib, int len,
>  		new = krealloc(work->iov,
>  			       sizeof(struct kvec) * work->iov_alloc_cnt,
>  			       GFP_KERNEL | __GFP_ZERO);
> -		if (!new)
> +		if (!new) {
> +			kfree(ar);
> +			work->iov_alloc_cnt -= 4;
>  			return -ENOMEM;
> +		}
>  		work->iov = new;
>  	}
>  

A few lines above, ar is allocated inside the 'if (aux_size)' block.
If aux_size is falsy, isn't it possible that ar will be NULL hence
we should have 'if (ar) kfree(ar);'?