[Mesa-dev] [PATCH mesa] move variable-sized struct at the end of parent struct

[Lionel Landwerlin]

On 01/11/2018 11:59, andrey simiklit wrote:
> Hello,
>
> Please find my comments below:
>
> On Thu, Nov 1, 2018 at 12:24 PM Eric Engestrom 
> <eric.engestrom at intel.com <mailto:eric.engestrom at intel.com>> wrote:
>
>       warning: field 'base' with variable sized type 'struct
>     drm_i915_query_topology_info'
>       not at the end of a struct or class is a GNU extension
>     [-Wgnu-variable-sized-type-not-at-end]
>
>     Signed-off-by: Eric Engestrom <eric.engestrom at intel.com
>     <mailto:eric.engestrom at intel.com>>
>     ---
>      src/intel/dev/gen_device_info.c | 2 +-
>      1 file changed, 1 insertion(+), 1 deletion(-)
>
>     diff --git a/src/intel/dev/gen_device_info.c
>     b/src/intel/dev/gen_device_info.c
>     index 5dbd06075722f8cc644e..242fe163447a4265acfb 100644
>     --- a/src/intel/dev/gen_device_info.c
>     +++ b/src/intel/dev/gen_device_info.c
>     @@ -991,8 +991,8 @@ gen_device_info_update_from_masks(struct
>     gen_device_info *devinfo,
>                                        uint32_t n_eus)
>      {
>         struct {
>     -      struct drm_i915_query_topology_info base;
>            uint8_t data[100];
>     +      struct drm_i915_query_topology_info base;
>         } topology;
>
>
> I can be wrong, but it seems like here the 'data[100]' field should 
> rather be placed after the 'base' field
> because it was done as far as I understood to allocate memory on the stack
> for the 'drm_i915_query_topology_info::data[]' field. I guess that 
> this patch
> may introduce the stack corruption on the following line:
>    for (int b = 0; b < topology.base.subslice_offset; b++)
>       topology.base.data[b] = (slice_mask >> (b * 8)) & 0xff;


Andrey's right, the base field needs to be first and data following.

nack :(


>
>         assert((slice_mask & 0xff) == slice_mask);
>     -- 
>     Cheers,
>       Eric
>
>     _______________________________________________
>     mesa-dev mailing list
>     mesa-dev at lists.freedesktop.org <mailto:mesa-dev at lists.freedesktop.org>
>     https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
>
> Regards,
> Andrii.
>
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