[PATCH] scsi: myrb: fix sprintf buffer overflow warning

[PATCH] scsi: myrb: fix sprintf buffer overflow warning

[Arnd Bergmann]

gcc warns that the 12 byte fw_version field might not be long enough to
contain the generated firmware name string:

drivers/scsi/myrb.c: In function 'myrb_get_hba_config':
drivers/scsi/myrb.c:1052:38: error: '%02d' directive writing between 2 and 3 bytes into a region of size between 2 and 5 [-Werror=format-overflow=]
  sprintf(cb->fw_version, "%d.%02d-%c-%02d",
                                      ^~~~
drivers/scsi/myrb.c:1052:26: note: directive argument in the range [0, 255]
  sprintf(cb->fw_version, "%d.%02d-%c-%02d",
                          ^~~~~~~~~~~~~~~~~
drivers/scsi/myrb.c:1052:2: note: 'sprintf' output between 10 and 14 bytes into a destination of size 12
  sprintf(cb->fw_version, "%d.%02d-%c-%02d",
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   enquiry2->fw.major_version,
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   enquiry2->fw.minor_version,
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   enquiry2->fw.firmware_type,
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   enquiry2->fw.turn_id);
   ~~~~~~~~~~~~~~~~~~~~~

I have not checked whether there are appropriate range checks before the
sprintf, but there is a range check after it that will bail out in case
of out of range version numbers. This means we can simply use snprintf()
instead of sprintf() to limit the output buffer size, and it will work
correctly.

Fixes: 081ff398c56c ("scsi: myrb: Add Mylex RAID controller (block interface)")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/scsi/myrb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/myrb.c b/drivers/scsi/myrb.c
index aeb282f617c5..0642f2d0a3bb 100644
--- a/drivers/scsi/myrb.c
+++ b/drivers/scsi/myrb.c
@@ -1049,7 +1049,8 @@ static int myrb_get_hba_config(struct myrb_hba *cb)
 		enquiry2->fw.firmware_type = '0';
 		enquiry2->fw.turn_id = 0;
 	}
-	sprintf(cb->fw_version, "%d.%02d-%c-%02d",
+	snprintf(cb->fw_version, sizeof(cb->fw_version),
+		"%d.%02d-%c-%02d",
 		enquiry2->fw.major_version,
 		enquiry2->fw.minor_version,
 		enquiry2->fw.firmware_type,
-- 
2.18.0

Re: [PATCH] scsi: myrb: fix sprintf buffer overflow warning

[Hannes Reinecke]

On 11/2/18 4:34 PM, Arnd Bergmann wrote:
> gcc warns that the 12 byte fw_version field might not be long enough to
> contain the generated firmware name string:
> 
> drivers/scsi/myrb.c: In function 'myrb_get_hba_config':
> drivers/scsi/myrb.c:1052:38: error: '%02d' directive writing between 2 and 3 bytes into a region of size between 2 and 5 [-Werror=format-overflow=]
>    sprintf(cb->fw_version, "%d.%02d-%c-%02d",
>                                        ^~~~
> drivers/scsi/myrb.c:1052:26: note: directive argument in the range [0, 255]
>    sprintf(cb->fw_version, "%d.%02d-%c-%02d",
>                            ^~~~~~~~~~~~~~~~~
> drivers/scsi/myrb.c:1052:2: note: 'sprintf' output between 10 and 14 bytes into a destination of size 12
>    sprintf(cb->fw_version, "%d.%02d-%c-%02d",
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     enquiry2->fw.major_version,
>     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     enquiry2->fw.minor_version,
>     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     enquiry2->fw.firmware_type,
>     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     enquiry2->fw.turn_id);
>     ~~~~~~~~~~~~~~~~~~~~~
> 
> I have not checked whether there are appropriate range checks before the
> sprintf, but there is a range check after it that will bail out in case
> of out of range version numbers. This means we can simply use snprintf()
> instead of sprintf() to limit the output buffer size, and it will work
> correctly.
> 
> Fixes: 081ff398c56c ("scsi: myrb: Add Mylex RAID controller (block interface)")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   drivers/scsi/myrb.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/myrb.c b/drivers/scsi/myrb.c
> index aeb282f617c5..0642f2d0a3bb 100644
> --- a/drivers/scsi/myrb.c
> +++ b/drivers/scsi/myrb.c
> @@ -1049,7 +1049,8 @@ static int myrb_get_hba_config(struct myrb_hba *cb)
>   		enquiry2->fw.firmware_type = '0';
>   		enquiry2->fw.turn_id = 0;
>   	}
> -	sprintf(cb->fw_version, "%d.%02d-%c-%02d",
> +	snprintf(cb->fw_version, sizeof(cb->fw_version),
> +		"%d.%02d-%c-%02d",
>   		enquiry2->fw.major_version,
>   		enquiry2->fw.minor_version,
>   		enquiry2->fw.firmware_type,
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes

Re: [PATCH] scsi: myrb: fix sprintf buffer overflow warning

[Martin K. Petersen]

Arnd,

> gcc warns that the 12 byte fw_version field might not be long enough to
> contain the generated firmware name string:

Applied to 4.20/scsi-fixes, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering