Re: [FFmpeg-devel] [PATCH] avocdec/cavsdsp: Fix undefined pointer arithmetic

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Andreas Rheinhardt:
> src2 is used in CAVS_SUBPIX_HV iff FULL is true (it is exactly
> for the egpr functions); otherwise it might be NULL. So check
> for FULL before doing pointer arithmetic.
> Fixes a "src/libavcodec/cavsdsp.c:524:1: runtime error: applying
> non-zero offset 8 to null pointer" from UBSan.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
>  libavcodec/cavsdsp.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/libavcodec/cavsdsp.c b/libavcodec/cavsdsp.c
> index af46eaf8d2..69420242d6 100644
> --- a/libavcodec/cavsdsp.c
> +++ b/libavcodec/cavsdsp.c
> @@ -425,13 +425,14 @@ static void OPNAME ## cavs_filt8_hv_ ## NAME(uint8_t *dst, const uint8_t *src1,
>  \
>  static void OPNAME ## cavs_filt16_hv_ ## NAME(uint8_t *dst, const uint8_t *src1, const uint8_t *src2, ptrdiff_t dstStride, ptrdiff_t srcStride)\
>  {                                                                       \
> -    OPNAME ## cavs_filt8_hv_ ## NAME(dst  , src1,   src2  , dstStride, srcStride); \
> -    OPNAME ## cavs_filt8_hv_ ## NAME(dst+8, src1+8, src2+8, dstStride, srcStride); \
> +    OPNAME ## cavs_filt8_hv_ ## NAME(dst  , src1,   FULL ? src2     : NULL, dstStride, srcStride); \
> +    OPNAME ## cavs_filt8_hv_ ## NAME(dst+8, src1+8, FULL ? src2 + 8 : NULL, dstStride, srcStride); \
>      src1 += 8*srcStride;\
> -    src2 += 8*srcStride;\
> +    if (FULL) \
> +        src2 += 8*srcStride;\
>      dst += 8*dstStride;\
> -    OPNAME ## cavs_filt8_hv_ ## NAME(dst  , src1,   src2  , dstStride, srcStride); \
> -    OPNAME ## cavs_filt8_hv_ ## NAME(dst+8, src1+8, src2+8, dstStride, srcStride); \
> +    OPNAME ## cavs_filt8_hv_ ## NAME(dst  , src1,   FULL ? src2     : NULL, dstStride, srcStride); \
> +    OPNAME ## cavs_filt8_hv_ ## NAME(dst+8, src1+8, FULL ? src2 + 8 : NULL, dstStride, srcStride); \
>  }\
>  
>  #define CAVS_MC(OPNAME, SIZE) \
> @@ -492,22 +493,22 @@ static void OPNAME ## cavs_qpel ## SIZE ## _mc33_c(uint8_t *dst, const uint8_t *
>  \
>  static void OPNAME ## cavs_qpel ## SIZE ## _mc21_c(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)\
>  {\
> -  OPNAME ## cavs_filt ## SIZE ## _hv_ff(dst, src, src+stride+1,stride, stride); \
> +  OPNAME ## cavs_filt ## SIZE ## _hv_ff(dst, src, NULL, stride, stride); \
>  }\
>  \
>  static void OPNAME ## cavs_qpel ## SIZE ## _mc12_c(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)\
>  {\
> -  OPNAME ## cavs_filt ## SIZE ## _hv_ii(dst, src, src+stride+1,stride, stride); \
> +  OPNAME ## cavs_filt ## SIZE ## _hv_ii(dst, src, NULL, stride, stride); \
>  }\
>  \
>  static void OPNAME ## cavs_qpel ## SIZE ## _mc32_c(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)\
>  {\
> -  OPNAME ## cavs_filt ## SIZE ## _hv_kk(dst, src, src+stride+1,stride, stride); \
> +  OPNAME ## cavs_filt ## SIZE ## _hv_kk(dst, src, NULL, stride, stride); \
>  }\
>  \
>  static void OPNAME ## cavs_qpel ## SIZE ## _mc23_c(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)\
>  {\
> -  OPNAME ## cavs_filt ## SIZE ## _hv_qq(dst, src, src+stride+1,stride, stride); \
> +  OPNAME ## cavs_filt ## SIZE ## _hv_qq(dst, src, NULL, stride, stride); \
>  }\
>  
>  #define op_put1(a, b)  a = cm[((b)+4)>>3]

Will apply this patch tomorrow unless there are objections.

- Andreas

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