linux-hardening - Re: [PATCH v3][next] scsi: smartpqi: Replace one-element array with flexible-array member

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Date:   Tue, 7 Feb 2023 15:01:19 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Don Brace <don.brace@...rochip.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        storagedev@...rochip.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3][next] scsi: smartpqi: Replace one-element array with
 flexible-array member

On Tue, Feb 07, 2023 at 03:59:43PM -0600, Gustavo A. R. Silva wrote:
> One-element arrays are deprecated, and we are replacing them with flexible
> array members instead. So, replace one-element array with flexible-array
> member in struct report_log_lun_list.
> 
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE routines
> on memcpy().
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/204
> Acked-by: Don Brace <don.brace@...rochip.com>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Looks good to me -- both before and after, there is 1 extra all-zero
entry at the end. But now the struct is using a flex array correctly.

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
> Changes in v3:
>  - Amplify the existing comment instead of adding a new one. By Don
>    Brace[1].
>  - Add Don's Acked-by tag to the changelog.
>    Link: https://lore.kernel.org/linux-hardening/d881ad98-a291-1c9b-53dc-199f23f1625e@embeddedor.com/ [1]
> 
> Changes in v2:
>  - In v1 we thought that the original code was allocating one too-many
>    entries for the list. However, Don Brace commented that the allocation
>    was actually intentional[2]. So, I added a code comment with his feedback.
>    Link: https://lore.kernel.org/linux-hardening/16e6c434-44af-2efb-d4bc-a253e93e5590@embeddedor.com/  [2]
> 
> v1:
>  - Link: https://lore.kernel.org/linux-hardening/c80c0979933e0c05e80d95792ef167a28640a14b.1663816572.git.gustavoars@kernel.org/
> 
>  drivers/scsi/smartpqi/smartpqi.h      | 2 +-
>  drivers/scsi/smartpqi/smartpqi_init.c | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/smartpqi/smartpqi.h b/drivers/scsi/smartpqi/smartpqi.h
> index af27bb0f3133..228838eb3686 100644
> --- a/drivers/scsi/smartpqi/smartpqi.h
> +++ b/drivers/scsi/smartpqi/smartpqi.h
> @@ -954,7 +954,7 @@ struct report_log_lun {
>  
>  struct report_log_lun_list {
>  	struct report_lun_header header;
> -	struct report_log_lun lun_entries[1];
> +	struct report_log_lun lun_entries[];
>  };
>  
>  struct report_phys_lun_8byte_wwid {
> diff --git a/drivers/scsi/smartpqi/smartpqi_init.c b/drivers/scsi/smartpqi/smartpqi_init.c
> index d0446d4d4465..49a8f91810b6 100644
> --- a/drivers/scsi/smartpqi/smartpqi_init.c
> +++ b/drivers/scsi/smartpqi/smartpqi_init.c
> @@ -1259,7 +1259,8 @@ static int pqi_get_device_lists(struct pqi_ctrl_info *ctrl_info,
>  			"report logical LUNs failed\n");
>  
>  	/*
> -	 * Tack the controller itself onto the end of the logical device list.
> +	 * Tack the controller itself onto the end of the logical device list
> +	 * by adding a list entry that is all zeros.
>  	 */
>  
>  	logdev_data = *logdev_list;
> -- 
> 2.34.1
> 

-- 
Kees Cook