[v2,1/2] media: staging/intel-ipu3: css: Fix wrong size comparison

  There is a wrong comparison of the total size of the loaded firmware
css->fw->size with the size of a pointer to struct imgu_fw_header.

Fix this by using the right operand 'struct imgu_fw_header' for
sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
into a flexible-array member. Also, adjust the relational operator
to be '<=' instead of '<', as it seems that the intention of the
comparison is to determine if the loaded firmware contains any
'struct imgu_fw_info' items in the binary_header[] array than merely
the file_header (struct imgu_fw_bi_file_h).

The replacement of the one-element array with a flexible-array member
also help with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---

It'd be just great if someone that knows this code better can confirm
these changes are correct. In particular the adjustment of the
relational operator. Thanks!

Changes in v2:
 - Use flexible array and adjust relational operator, accordingly.
 - Update changelog text.

 drivers/staging/media/ipu3/ipu3-css-fw.c | 2 +-
 drivers/staging/media/ipu3/ipu3-css-fw.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
  

Hi Gustavo,

I missed you already had sent v2...

On Fri, Jul 30, 2021 at 07:08:13AM -0500, Gustavo A. R. Silva wrote:
> There is a wrong comparison of the total size of the loaded firmware
> css->fw->size with the size of a pointer to struct imgu_fw_header.
> 
> Fix this by using the right operand 'struct imgu_fw_header' for
> sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
> into a flexible-array member. Also, adjust the relational operator
> to be '<=' instead of '<', as it seems that the intention of the
> comparison is to determine if the loaded firmware contains any
> 'struct imgu_fw_info' items in the binary_header[] array than merely
> the file_header (struct imgu_fw_bi_file_h).
> 
> The replacement of the one-element array with a flexible-array member
> also help with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
> Cc: stable@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> 
> It'd be just great if someone that knows this code better can confirm
> these changes are correct. In particular the adjustment of the
> relational operator. Thanks!
> 
> Changes in v2:
>  - Use flexible array and adjust relational operator, accordingly.

The operator was just correct. The check is just there to see the firmware
is at least as large as the struct as which it is being accessed.

>  - Update changelog text.
> 
>  drivers/staging/media/ipu3/ipu3-css-fw.c | 2 +-
>  drivers/staging/media/ipu3/ipu3-css-fw.h | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.c b/drivers/staging/media/ipu3/ipu3-css-fw.c
> index 45aff76198e2..630cb5186b48 100644
> --- a/drivers/staging/media/ipu3/ipu3-css-fw.c
> +++ b/drivers/staging/media/ipu3/ipu3-css-fw.c
> @@ -124,7 +124,7 @@ int imgu_css_fw_init(struct imgu_css *css)
>  	/* Check and display fw header info */
>  
>  	css->fwp = (struct imgu_fw_header *)css->fw->data;
> -	if (css->fw->size < sizeof(struct imgu_fw_header *) ||
> +	if (css->fw->size <= sizeof(struct imgu_fw_header) ||
>  	    css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
>  		goto bad_fw;
>  	if (sizeof(struct imgu_fw_bi_file_h) +
> diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.h b/drivers/staging/media/ipu3/ipu3-css-fw.h
> index 3c078f15a295..c0bc57fd678a 100644
> --- a/drivers/staging/media/ipu3/ipu3-css-fw.h
> +++ b/drivers/staging/media/ipu3/ipu3-css-fw.h
> @@ -171,7 +171,7 @@ struct imgu_fw_bi_file_h {
>  
>  struct imgu_fw_header {
>  	struct imgu_fw_bi_file_h file_header;
> -	struct imgu_fw_info binary_header[1];	/* binary_nr items */
> +	struct imgu_fw_info binary_header[];	/* binary_nr items */
>  };
>  
>  /******************* Firmware functions *******************/
  

Hi Sakari,

On 8/2/21 01:05, Sakari Ailus wrote:
> Hi Gustavo,
> 
> I missed you already had sent v2...
> 
> On Fri, Jul 30, 2021 at 07:08:13AM -0500, Gustavo A. R. Silva wrote:
>> There is a wrong comparison of the total size of the loaded firmware
>> css->fw->size with the size of a pointer to struct imgu_fw_header.
>>
>> Fix this by using the right operand 'struct imgu_fw_header' for
>> sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
>> into a flexible-array member. Also, adjust the relational operator
>> to be '<=' instead of '<', as it seems that the intention of the
>> comparison is to determine if the loaded firmware contains any
>> 'struct imgu_fw_info' items in the binary_header[] array than merely
>> the file_header (struct imgu_fw_bi_file_h).
>>
>> The replacement of the one-element array with a flexible-array member
>> also help with the ongoing efforts to globally enable -Warray-bounds
>> and get us closer to being able to tighten the FORTIFY_SOURCE routines
>> on memcpy().
>>
>> Link: https://github.com/KSPP/linux/issues/79
>> Link: https://github.com/KSPP/linux/issues/109
>> Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>>
>> It'd be just great if someone that knows this code better can confirm
>> these changes are correct. In particular the adjustment of the
>> relational operator. Thanks!
>>
>> Changes in v2:
>>  - Use flexible array and adjust relational operator, accordingly.
> 
> The operator was just correct. The check is just there to see the firmware
> is at least as large as the struct as which it is being accessed.

I'm a bit confused, so based on your reply to v1 of this series, this patch
is now correct, right?

The operator in v1 _was_ correct as long as the one-element array wasn't
transformed into a flexible array, right?

Notice that generally speaking flexible-array members don't occupy space in the
containing structure:

$ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
struct imgu_fw_header {
	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
	struct imgu_fw_info        binary_header[] __attribute__((__aligned__(8))); /*    72     0 */

	/* size: 72, cachelines: 2, members: 2 */
	/* forced alignments: 1 */
	/* last cacheline: 8 bytes */
} __attribute__((__aligned__(8)));

$ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
struct imgu_fw_header {
	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
	struct imgu_fw_info        binary_header[1] __attribute__((__aligned__(8))); /*    72  1200 */

	/* size: 1272, cachelines: 20, members: 2 */
	/* forced alignments: 1 */
	/* last cacheline: 56 bytes */
} __attribute__((__aligned__(8)));

So, now that the flexible array transformation is included in the same patch as the
bugfix, the operator is changed from '<' to '<='

Can you please confirm if this v2 is now correct? if so, it'd be great to have your
Reviewed-by tag. :)

Thanks!
--
Gustavo

> 
>>  - Update changelog text.
>>
>>  drivers/staging/media/ipu3/ipu3-css-fw.c | 2 +-
>>  drivers/staging/media/ipu3/ipu3-css-fw.h | 2 +-
>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.c b/drivers/staging/media/ipu3/ipu3-css-fw.c
>> index 45aff76198e2..630cb5186b48 100644
>> --- a/drivers/staging/media/ipu3/ipu3-css-fw.c
>> +++ b/drivers/staging/media/ipu3/ipu3-css-fw.c
>> @@ -124,7 +124,7 @@ int imgu_css_fw_init(struct imgu_css *css)
>>  	/* Check and display fw header info */
>>  
>>  	css->fwp = (struct imgu_fw_header *)css->fw->data;
>> -	if (css->fw->size < sizeof(struct imgu_fw_header *) ||
>> +	if (css->fw->size <= sizeof(struct imgu_fw_header) ||
>>  	    css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
>>  		goto bad_fw;
>>  	if (sizeof(struct imgu_fw_bi_file_h) +
>> diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.h b/drivers/staging/media/ipu3/ipu3-css-fw.h
>> index 3c078f15a295..c0bc57fd678a 100644
>> --- a/drivers/staging/media/ipu3/ipu3-css-fw.h
>> +++ b/drivers/staging/media/ipu3/ipu3-css-fw.h
>> @@ -171,7 +171,7 @@ struct imgu_fw_bi_file_h {
>>  
>>  struct imgu_fw_header {
>>  	struct imgu_fw_bi_file_h file_header;
>> -	struct imgu_fw_info binary_header[1];	/* binary_nr items */
>> +	struct imgu_fw_info binary_header[];	/* binary_nr items */
>>  };
>>  
>>  /******************* Firmware functions *******************/
>
  

I missed that you change < sizeof() to <= sizeof()...  Sakari is right
that it should be < sizeof().  <= doesn't work at all ever.  If you
wanted a higher limit then the next limit woule be:

	if (css->fw->size < struct_size(css->fwp, binary_header, 1))

regards,
dan carpenter
  

Hi Gustavo,

Apologies for the delay.

On Mon, Aug 02, 2021 at 08:46:20AM -0500, Gustavo A. R. Silva wrote:
> Hi Sakari,
> 
> On 8/2/21 01:05, Sakari Ailus wrote:
> > Hi Gustavo,
> > 
> > I missed you already had sent v2...
> > 
> > On Fri, Jul 30, 2021 at 07:08:13AM -0500, Gustavo A. R. Silva wrote:
> >> There is a wrong comparison of the total size of the loaded firmware
> >> css->fw->size with the size of a pointer to struct imgu_fw_header.
> >>
> >> Fix this by using the right operand 'struct imgu_fw_header' for
> >> sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
> >> into a flexible-array member. Also, adjust the relational operator
> >> to be '<=' instead of '<', as it seems that the intention of the
> >> comparison is to determine if the loaded firmware contains any
> >> 'struct imgu_fw_info' items in the binary_header[] array than merely
> >> the file_header (struct imgu_fw_bi_file_h).
> >>
> >> The replacement of the one-element array with a flexible-array member
> >> also help with the ongoing efforts to globally enable -Warray-bounds
> >> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> >> on memcpy().
> >>
> >> Link: https://github.com/KSPP/linux/issues/79
> >> Link: https://github.com/KSPP/linux/issues/109
> >> Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
> >> Cc: stable@vger.kernel.org
> >> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> >> ---
> >>
> >> It'd be just great if someone that knows this code better can confirm
> >> these changes are correct. In particular the adjustment of the
> >> relational operator. Thanks!
> >>
> >> Changes in v2:
> >>  - Use flexible array and adjust relational operator, accordingly.
> > 
> > The operator was just correct. The check is just there to see the firmware
> > is at least as large as the struct as which it is being accessed.
> 
> I'm a bit confused, so based on your reply to v1 of this series, this patch
> is now correct, right?
> 
> The operator in v1 _was_ correct as long as the one-element array wasn't
> transformed into a flexible array, right?
> 
> Notice that generally speaking flexible-array members don't occupy space in the
> containing structure:
> 
> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
> struct imgu_fw_header {
> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> 	struct imgu_fw_info        binary_header[] __attribute__((__aligned__(8))); /*    72     0 */
> 
> 	/* size: 72, cachelines: 2, members: 2 */
> 	/* forced alignments: 1 */
> 	/* last cacheline: 8 bytes */
> } __attribute__((__aligned__(8)));
> 
> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
> struct imgu_fw_header {
> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> 	struct imgu_fw_info        binary_header[1] __attribute__((__aligned__(8))); /*    72  1200 */
> 
> 	/* size: 1272, cachelines: 20, members: 2 */
> 	/* forced alignments: 1 */
> 	/* last cacheline: 56 bytes */
> } __attribute__((__aligned__(8)));
> 
> So, now that the flexible array transformation is included in the same patch as the
> bugfix, the operator is changed from '<' to '<='

'<' is correct since you only need as much data as the struct you're about
to access is large, not a byte more than that. As Dan noted.

I think you could add a check for binary_nr is at least one.
  

Hi Sakari,

Please, see my comments below...

On 8/10/21 10:18, Sakari Ailus wrote:
> Hi Gustavo,
> 
> Apologies for the delay.
> 
> On Mon, Aug 02, 2021 at 08:46:20AM -0500, Gustavo A. R. Silva wrote:
>> Hi Sakari,
>>
>> On 8/2/21 01:05, Sakari Ailus wrote:
>>> Hi Gustavo,
>>>
>>> I missed you already had sent v2...
>>>
>>> On Fri, Jul 30, 2021 at 07:08:13AM -0500, Gustavo A. R. Silva wrote:
>>>> There is a wrong comparison of the total size of the loaded firmware
>>>> css->fw->size with the size of a pointer to struct imgu_fw_header.
>>>>
>>>> Fix this by using the right operand 'struct imgu_fw_header' for
>>>> sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
>>>> into a flexible-array member. Also, adjust the relational operator
>>>> to be '<=' instead of '<', as it seems that the intention of the
>>>> comparison is to determine if the loaded firmware contains any
>>>> 'struct imgu_fw_info' items in the binary_header[] array than merely
>>>> the file_header (struct imgu_fw_bi_file_h).
>>>>
>>>> The replacement of the one-element array with a flexible-array member
>>>> also help with the ongoing efforts to globally enable -Warray-bounds
>>>> and get us closer to being able to tighten the FORTIFY_SOURCE routines
>>>> on memcpy().
>>>>
>>>> Link: https://github.com/KSPP/linux/issues/79
>>>> Link: https://github.com/KSPP/linux/issues/109
>>>> Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
>>>> Cc: stable@vger.kernel.org
>>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>>> ---
>>>>
>>>> It'd be just great if someone that knows this code better can confirm
>>>> these changes are correct. In particular the adjustment of the
>>>> relational operator. Thanks!
>>>>
>>>> Changes in v2:
>>>>  - Use flexible array and adjust relational operator, accordingly.
>>>
>>> The operator was just correct. The check is just there to see the firmware
>>> is at least as large as the struct as which it is being accessed.
>>
>> I'm a bit confused, so based on your reply to v1 of this series, this patch
>> is now correct, right?
>>
>> The operator in v1 _was_ correct as long as the one-element array wasn't
>> transformed into a flexible array, right?
>>
>> Notice that generally speaking flexible-array members don't occupy space in the
>> containing structure:
>>
>> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
>> struct imgu_fw_header {
>> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
>> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
>> 	struct imgu_fw_info        binary_header[] __attribute__((__aligned__(8))); /*    72     0 */
>>
>> 	/* size: 72, cachelines: 2, members: 2 */
>> 	/* forced alignments: 1 */
>> 	/* last cacheline: 8 bytes */
>> } __attribute__((__aligned__(8)));
>>
>> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
>> struct imgu_fw_header {
>> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
>> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
>> 	struct imgu_fw_info        binary_header[1] __attribute__((__aligned__(8))); /*    72  1200 */
>>
>> 	/* size: 1272, cachelines: 20, members: 2 */
>> 	/* forced alignments: 1 */
>> 	/* last cacheline: 56 bytes */
>> } __attribute__((__aligned__(8)));
>>
>> So, now that the flexible array transformation is included in the same patch as the
>> bugfix, the operator is changed from '<' to '<='
> 
> '<' is correct since you only need as much data as the struct you're about
> to access is large, not a byte more than that. As Dan noted.
> 
> I think you could add a check for binary_nr is at least one.

If we need to check that binary_nr is at least one, then this would be the right
change:

        css->fwp = (struct imgu_fw_header *)css->fw->data;
-       if (css->fw->size < sizeof(struct imgu_fw_header *) ||
+       if (css->fw->size < struct_size(css->fwp, binary_header, 1) ||
            css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
                goto bad_fw;


--
Gustavo
  

On Tue, Aug 10, 2021 at 11:26:14AM -0500, Gustavo A. R. Silva wrote:
> Hi Sakari,
> 
> Please, see my comments below...
> 
> On 8/10/21 10:18, Sakari Ailus wrote:
> > Hi Gustavo,
> > 
> > Apologies for the delay.
> > 
> > On Mon, Aug 02, 2021 at 08:46:20AM -0500, Gustavo A. R. Silva wrote:
> >> Hi Sakari,
> >>
> >> On 8/2/21 01:05, Sakari Ailus wrote:
> >>> Hi Gustavo,
> >>>
> >>> I missed you already had sent v2...
> >>>
> >>> On Fri, Jul 30, 2021 at 07:08:13AM -0500, Gustavo A. R. Silva wrote:
> >>>> There is a wrong comparison of the total size of the loaded firmware
> >>>> css->fw->size with the size of a pointer to struct imgu_fw_header.
> >>>>
> >>>> Fix this by using the right operand 'struct imgu_fw_header' for
> >>>> sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
> >>>> into a flexible-array member. Also, adjust the relational operator
> >>>> to be '<=' instead of '<', as it seems that the intention of the
> >>>> comparison is to determine if the loaded firmware contains any
> >>>> 'struct imgu_fw_info' items in the binary_header[] array than merely
> >>>> the file_header (struct imgu_fw_bi_file_h).
> >>>>
> >>>> The replacement of the one-element array with a flexible-array member
> >>>> also help with the ongoing efforts to globally enable -Warray-bounds
> >>>> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> >>>> on memcpy().
> >>>>
> >>>> Link: https://github.com/KSPP/linux/issues/79
> >>>> Link: https://github.com/KSPP/linux/issues/109
> >>>> Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
> >>>> Cc: stable@vger.kernel.org
> >>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> >>>> ---
> >>>>
> >>>> It'd be just great if someone that knows this code better can confirm
> >>>> these changes are correct. In particular the adjustment of the
> >>>> relational operator. Thanks!
> >>>>
> >>>> Changes in v2:
> >>>>  - Use flexible array and adjust relational operator, accordingly.
> >>>
> >>> The operator was just correct. The check is just there to see the firmware
> >>> is at least as large as the struct as which it is being accessed.
> >>
> >> I'm a bit confused, so based on your reply to v1 of this series, this patch
> >> is now correct, right?
> >>
> >> The operator in v1 _was_ correct as long as the one-element array wasn't
> >> transformed into a flexible array, right?
> >>
> >> Notice that generally speaking flexible-array members don't occupy space in the
> >> containing structure:
> >>
> >> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
> >> struct imgu_fw_header {
> >> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
> >> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> >> 	struct imgu_fw_info        binary_header[] __attribute__((__aligned__(8))); /*    72     0 */
> >>
> >> 	/* size: 72, cachelines: 2, members: 2 */
> >> 	/* forced alignments: 1 */
> >> 	/* last cacheline: 8 bytes */
> >> } __attribute__((__aligned__(8)));
> >>
> >> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
> >> struct imgu_fw_header {
> >> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
> >> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> >> 	struct imgu_fw_info        binary_header[1] __attribute__((__aligned__(8))); /*    72  1200 */
> >>
> >> 	/* size: 1272, cachelines: 20, members: 2 */
> >> 	/* forced alignments: 1 */
> >> 	/* last cacheline: 56 bytes */
> >> } __attribute__((__aligned__(8)));
> >>
> >> So, now that the flexible array transformation is included in the same patch as the
> >> bugfix, the operator is changed from '<' to '<='
> > 
> > '<' is correct since you only need as much data as the struct you're about
> > to access is large, not a byte more than that. As Dan noted.
> > 
> > I think you could add a check for binary_nr is at least one.
> 
> If we need to check that binary_nr is at least one, then this would be the right
> change:
> 
>         css->fwp = (struct imgu_fw_header *)css->fw->data;
> -       if (css->fw->size < sizeof(struct imgu_fw_header *) ||
> +       if (css->fw->size < struct_size(css->fwp, binary_header, 1) ||
>             css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
>                 goto bad_fw;

There's already a check the space required for the array of binary_nr is
there. But not the number itself.
  

On 8/10/21 11:30, Sakari Ailus wrote:
> On Tue, Aug 10, 2021 at 11:26:14AM -0500, Gustavo A. R. Silva wrote:
>> Hi Sakari,
>>
>> Please, see my comments below...
>>
>> On 8/10/21 10:18, Sakari Ailus wrote:
>>> Hi Gustavo,
>>>
>>> Apologies for the delay.
>>>
>>> On Mon, Aug 02, 2021 at 08:46:20AM -0500, Gustavo A. R. Silva wrote:
>>>> Hi Sakari,
>>>>
>>>> On 8/2/21 01:05, Sakari Ailus wrote:
>>>>> Hi Gustavo,
>>>>>
>>>>> I missed you already had sent v2...
>>>>>
>>>>> On Fri, Jul 30, 2021 at 07:08:13AM -0500, Gustavo A. R. Silva wrote:
>>>>>> There is a wrong comparison of the total size of the loaded firmware
>>>>>> css->fw->size with the size of a pointer to struct imgu_fw_header.
>>>>>>
>>>>>> Fix this by using the right operand 'struct imgu_fw_header' for
>>>>>> sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
>>>>>> into a flexible-array member. Also, adjust the relational operator
>>>>>> to be '<=' instead of '<', as it seems that the intention of the
>>>>>> comparison is to determine if the loaded firmware contains any
>>>>>> 'struct imgu_fw_info' items in the binary_header[] array than merely
>>>>>> the file_header (struct imgu_fw_bi_file_h).
>>>>>>
>>>>>> The replacement of the one-element array with a flexible-array member
>>>>>> also help with the ongoing efforts to globally enable -Warray-bounds
>>>>>> and get us closer to being able to tighten the FORTIFY_SOURCE routines
>>>>>> on memcpy().
>>>>>>
>>>>>> Link: https://github.com/KSPP/linux/issues/79
>>>>>> Link: https://github.com/KSPP/linux/issues/109
>>>>>> Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
>>>>>> Cc: stable@vger.kernel.org
>>>>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>>>>> ---
>>>>>>
>>>>>> It'd be just great if someone that knows this code better can confirm
>>>>>> these changes are correct. In particular the adjustment of the
>>>>>> relational operator. Thanks!
>>>>>>
>>>>>> Changes in v2:
>>>>>>  - Use flexible array and adjust relational operator, accordingly.
>>>>>
>>>>> The operator was just correct. The check is just there to see the firmware
>>>>> is at least as large as the struct as which it is being accessed.
>>>>
>>>> I'm a bit confused, so based on your reply to v1 of this series, this patch
>>>> is now correct, right?
>>>>
>>>> The operator in v1 _was_ correct as long as the one-element array wasn't
>>>> transformed into a flexible array, right?
>>>>
>>>> Notice that generally speaking flexible-array members don't occupy space in the
>>>> containing structure:
>>>>
>>>> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
>>>> struct imgu_fw_header {
>>>> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
>>>> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
>>>> 	struct imgu_fw_info        binary_header[] __attribute__((__aligned__(8))); /*    72     0 */
>>>>
>>>> 	/* size: 72, cachelines: 2, members: 2 */
>>>> 	/* forced alignments: 1 */
>>>> 	/* last cacheline: 8 bytes */
>>>> } __attribute__((__aligned__(8)));
>>>>
>>>> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
>>>> struct imgu_fw_header {
>>>> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
>>>> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
>>>> 	struct imgu_fw_info        binary_header[1] __attribute__((__aligned__(8))); /*    72  1200 */
>>>>
>>>> 	/* size: 1272, cachelines: 20, members: 2 */
>>>> 	/* forced alignments: 1 */
>>>> 	/* last cacheline: 56 bytes */
>>>> } __attribute__((__aligned__(8)));
>>>>
>>>> So, now that the flexible array transformation is included in the same patch as the
>>>> bugfix, the operator is changed from '<' to '<='
>>>
>>> '<' is correct since you only need as much data as the struct you're about
>>> to access is large, not a byte more than that. As Dan noted.
>>>
>>> I think you could add a check for binary_nr is at least one.
>>
>> If we need to check that binary_nr is at least one, then this would be the right
>> change:
>>
>>         css->fwp = (struct imgu_fw_header *)css->fw->data;
>> -       if (css->fw->size < sizeof(struct imgu_fw_header *) ||
>> +       if (css->fw->size < struct_size(css->fwp, binary_header, 1) ||
>>             css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
>>                 goto bad_fw;
> 
> There's already a check the space required for the array of binary_nr is
> there. But not the number itself.

Yep; and that is for the upper limit.

The whole fix would be this:

diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.c b/drivers/staging/media/ipu3/ipu3-css-fw.c
index 45aff76198e2..8830f42f2b12 100644
--- a/drivers/staging/media/ipu3/ipu3-css-fw.c
+++ b/drivers/staging/media/ipu3/ipu3-css-fw.c
@@ -124,12 +124,11 @@ int imgu_css_fw_init(struct imgu_css *css)
        /* Check and display fw header info */

        css->fwp = (struct imgu_fw_header *)css->fw->data;
-       if (css->fw->size < sizeof(struct imgu_fw_header *) ||
+       if (css->fw->size < struct_size(css->fwp, binary_header, 1) ||
            css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
                goto bad_fw;
-       if (sizeof(struct imgu_fw_bi_file_h) +
-           css->fwp->file_header.binary_nr * sizeof(struct imgu_fw_info) >
-           css->fw->size)
+       if (struct_size((struct imgu_fw_header *)0, binary_header,
+                       css->fwp->file_header.binary_nr) > css->fw->size)
                goto bad_fw;

        dev_info(dev, "loaded firmware version %.64s, %u binaries, %zu bytes\n",
diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.h b/drivers/staging/media/ipu3/ipu3-css-fw.h
index 3c078f15a295..c0bc57fd678a 100644
--- a/drivers/staging/media/ipu3/ipu3-css-fw.h
+++ b/drivers/staging/media/ipu3/ipu3-css-fw.h
@@ -171,7 +171,7 @@ struct imgu_fw_bi_file_h {

 struct imgu_fw_header {
        struct imgu_fw_bi_file_h file_header;
-       struct imgu_fw_info binary_header[1];   /* binary_nr items */
+       struct imgu_fw_info binary_header[];    /* binary_nr items */
 };

 /******************* Firmware functions *******************/


Notice that "css->fw->size < struct_size(css->fwp, binary_header, 1)" with binary_header declared as a flexible-array
member is equivalent to "css->fw->size < sizeof(struct imgu_fw_header)" with binary_header declared as a one-element
array.

--
Gustavo