linux-hardening - Re: [PATCH] scsi: lpfc: Use struct_group to isolate cast to larger object

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Date:   Thu, 9 Dec 2021 06:50:23 -0800
From:   James Smart <jsmart2021@...il.com>
To:     Kees Cook <keescook@...omium.org>,
        James Smart <james.smart@...adcom.com>
Cc:     Dick Kennedy <dick.kennedy@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] scsi: lpfc: Use struct_group to isolate cast to larger
 object

On 12/3/2021 2:33 PM, Kees Cook wrote:
> When building under -Warray-bounds, a warning is generated when casting
> a u32 into MAILBOX_t (which is larger). This warning is conservative, but
> it's not an unreasonable change to make to improve future robustness. Use
> a tagged struct_group that can refer to either the specific fields or
> the first u32 separately, silencing this warning:
> 
> drivers/scsi/lpfc/lpfc_sli.c: In function 'lpfc_reset_barrier':
> drivers/scsi/lpfc/lpfc_sli.c:4787:29: error: array subscript 'MAILBOX_t[0]' is partly outside array bounds of 'volatile uint32_t[1]' {aka 'volatile unsigned int[1]'} [-Werror=array-bounds]
>   4787 |         ((MAILBOX_t *)&mbox)->mbxCommand = MBX_KILL_BOARD;
>        |                             ^~
> drivers/scsi/lpfc/lpfc_sli.c:4752:27: note: while referencing 'mbox'
>   4752 |         volatile uint32_t mbox;
>        |                           ^~~~
> 
> There is no change to the resulting executable instruction code.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---

looks fine.

Reviewed-by: James Smart <jsmart2021@...il.com>

-- james