[FFmpeg-devel] [PATCH v1] lavc/vvc: Validate num_signalled_palette_entries

[Frank Plowman]

On 18/05/2025 02:42, Nuo Mi wrote:
> Hi Frank,
> 👍,your fuzzing infrastructure caught this issue as well.
> How about this:
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20250517055150.807683-1-nuomi2021@gmail.com/

Sorry, I missed this.  Your patch looks good to me: probably preferable
in that it also validates the predicted size by the looks of it
(although I don't have a stream which exercises this aspect).

> 
> On Sun, May 18, 2025 at 5:05 AM Frank Plowman <post at frankplowman.com> wrote:
> 
>> "The value of CurrentPaletteSize[ startComp ] shall be in the range of 0
>> to maxNumPaletteEntries, inclusive."
>>
>> Signed-off-by: Frank Plowman <post at frankplowman.com>
>> ---
>>  libavcodec/vvc/ctu.c | 14 +++++++++++---
>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/libavcodec/vvc/ctu.c b/libavcodec/vvc/ctu.c
>> index 62c9d4f5c0..70800ba5fa 100644
>> --- a/libavcodec/vvc/ctu.c
>> +++ b/libavcodec/vvc/ctu.c
>> @@ -20,6 +20,7 @@
>>   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
>> 02110-1301 USA
>>   */
>>
>> +#include "libavutil/error.h"
>>  #include "libavutil/refstruct.h"
>>
>>  #include "cabac.h"
>> @@ -1873,7 +1874,7 @@ static void palette_predicted(VVCLocalContext *lc,
>> const bool local_dual_tree, i
>>          cu->plt[c].size = nb_predicted;
>>  }
>>
>> -static void palette_signaled(VVCLocalContext *lc, const bool
>> local_dual_tree,
>> +static int palette_signaled(VVCLocalContext *lc, const bool
>> local_dual_tree,
>>      const int start, const int end, const int max_entries)
>>  {
>>      const VVCSPS *sps         = lc->fc->ps.sps;
>> @@ -1883,6 +1884,9 @@ static void palette_signaled(VVCLocalContext *lc,
>> const bool local_dual_tree,
>>      const int size            = nb_predicted + nb_signaled;
>>      const bool dual_tree_luma = local_dual_tree && cu->tree_type ==
>> DUAL_TREE_LUMA;
>>
>> +    if (size > max_entries)
>> +        return AVERROR_INVALIDDATA;
>> +
>>      for (int c = start; c < end; c++) {
>>          Palette *plt = cu->plt + c;
>>          for (int i = nb_predicted; i < size; i++) {
>> @@ -1894,6 +1898,8 @@ static void palette_signaled(VVCLocalContext *lc,
>> const bool local_dual_tree,
>>          }
>>          plt->size = size;
>>      }
>> +
>> +    return 0;
>>  }
>>
>>  static void palette_update_predictor(VVCLocalContext *lc, const bool
>> local_dual_tree, int start, int end,
>> @@ -2070,7 +2076,7 @@ static int hls_palette_coding(VVCLocalContext *lc,
>> const VVCTreeType tree_type)
>>      int max_index                 = 0;
>>      int prev_run_pos              = 0;
>>
>> -    int predictor_size, start, end;
>> +    int predictor_size, start, end, ret;
>>      bool reused[VVC_MAX_NUM_PALETTE_PREDICTOR_SIZE];
>>      uint8_t run_type[MAX_PALETTE_CU_SIZE * MAX_PALETTE_CU_SIZE];
>>      uint8_t index[MAX_PALETTE_CU_SIZE * MAX_PALETTE_CU_SIZE];
>> @@ -2083,7 +2089,9 @@ static int hls_palette_coding(VVCLocalContext *lc,
>> const VVCTreeType tree_type)
>>      predictor_size = pp[start].size;
>>      memset(reused, 0, sizeof(reused[0]) * predictor_size);
>>      palette_predicted(lc, local_dual_tree, start, end, reused,
>> predictor_size, max_entries);
>> -    palette_signaled(lc, local_dual_tree, start, end, max_entries);
>> +    ret = palette_signaled(lc, local_dual_tree, start, end, max_entries);
>> +    if (ret < 0)
>> +        return ret;
>>      palette_update_predictor(lc, local_dual_tree, start, end, reused,
>> predictor_size);
>>
>>      if (cu->plt[start].size > 0)
>> --
>> 2.47.0
>>
>>
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