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Message-ID: <20210927144838.GA168427@embeddedor>
Date: Mon, 27 Sep 2021 09:48:38 -0500
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Len Baker <len.baker@....com>
Cc: Matthew Wilcox <willy@...radead.org>,
Hannes Reinecke <hare@...e.com>,
"James E.J. Bottomley" <jejb@...ux.ibm.com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Kees Cook <keescook@...omium.org>,
linux-hardening@...r.kernel.org, linux-scsi@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] scsi: advansys: Prefer struct_size over open coded
arithmetic
On Sat, Sep 25, 2021 at 01:42:05PM +0200, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + count * size" in the kzalloc() function.
>
> This code was detected with the help of Coccinelle and audited and fixed
> manually.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <len.baker@....com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
> Changelog v1 -> v2
> - Rebase against v5.15-rc2
Don't use mainline for these sorts of patches . Use linux-next instead:
https://www.kernel.org/doc/man-pages/linux-next.html
Thanks
--
Gustavo
> - Remove the unnecessary "size" variable (Gustavo A. R. Silva).
> - Update the commit changelog to inform that this code was detected
> using a Coccinelle script (Gustavo A. R. Silva).
>
> drivers/scsi/advansys.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c
> index ffb391967573..e341b3372482 100644
> --- a/drivers/scsi/advansys.c
> +++ b/drivers/scsi/advansys.c
> @@ -7477,8 +7477,8 @@ static int asc_build_req(struct asc_board *boardp, struct scsi_cmnd *scp,
> return ASC_ERROR;
> }
>
> - asc_sg_head = kzalloc(sizeof(asc_scsi_q->sg_head) +
> - use_sg * sizeof(struct asc_sg_list), GFP_ATOMIC);
> + asc_sg_head = kzalloc(struct_size(asc_sg_head, sg_list, use_sg),
> + GFP_ATOMIC);
> if (!asc_sg_head) {
> scsi_dma_unmap(scp);
> set_host_byte(scp, DID_SOFT_ERROR);
> --
> 2.25.1
>
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