linux-hardening - Re: [PATCH 8/8][next] scsi: aacraid: Replace one-element array with flexible-array member in struct aac

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Date:   Thu, 23 Jun 2022 09:29:25 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 8/8][next] scsi: aacraid: Replace one-element array with
 flexible-array member in struct aac_aifcmd

On Tue, Feb 22, 2022 at 01:31:07AM -0600, Gustavo A. R. Silva wrote:
> Replace one-element array with flexible-array member in struct
> aac_aifcmd.
> 
> This issue was found with the help of Coccinelle and audited and fixed,
> manually.
> 
> Link: https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
> Link: https://github.com/KSPP/linux/issues/79
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  drivers/scsi/aacraid/aacraid.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/aacraid/aacraid.h b/drivers/scsi/aacraid/aacraid.h
> index 97948cd5f13c..447feabf5360 100644
> --- a/drivers/scsi/aacraid/aacraid.h
> +++ b/drivers/scsi/aacraid/aacraid.h
> @@ -2616,7 +2616,7 @@ struct aac_hba_info {
>  struct aac_aifcmd {
>  	__le32 command;		/* Tell host what type of notify this is */
>  	__le32 seqnum;		/* To allow ordering of reports (if necessary) */
> -	u8 data[1];		/* Undefined length (from kernel viewpoint) */
> +	u8 data[];		/* Undefined length (from kernel viewpoint) */
>  };
>  
>  /**
> -- 
> 2.27.0
> 

FWIW, this patch solves an -Warray-bounds warning that is seen under
-fstrict-flex-arrays=3 (coming soon[1]):

../drivers/scsi/aacraid/commsup.c:1166:17: warning: array index 1 is past the end of the array (which contains 1 element) [-Warray-bounds]
                                (((__le32 *)aifcmd->data)[1] == cpu_to_le32(3));
                                            ^             ~
../drivers/scsi/aacraid/aacraid.h:2620:2: note: array 'data' declared here
        u8 data[1];             /* Undefined length (from kernel viewpoint) */
        ^
../drivers/scsi/aacraid/commsup.c:1286:20: warning: array index 3 is past the end of the array (which contains 1 element) [-Warray-bounds]
                                  ((((__le32 *)aifcmd->data)[3]
                                               ^             ~
../drivers/scsi/aacraid/aacraid.h:2620:2: note: array 'data' declared here
        u8 data[1];             /* Undefined length (from kernel viewpoint) */
        ^

[1] new flag in GCC and Clang:
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
    https://reviews.llvm.org/D126864


-- 
Kees Cook