indeo4: Decode all or nothing of a band header.
authorMichael Niedermayer <michael@niedermayer.cc>
Thu, 17 May 2018 11:40:38 +0000 (13:40 +0200)
committerMichael Niedermayer <michael@niedermayer.cc>
Fri, 25 May 2018 22:54:55 +0000 (00:54 +0200)
This avoids inconsistent value combinations.
Alternatively it would be possible to add more checks and careful use of
temporary variables, but my try of this quickly seemed to become
a rather large change.
The disadvantage of this, is that the struct is copied back and forth.

Fixes: index 6 out of bounds for type 'const uint16_t [5][16]'
Fixes: 6557/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_INDEO4_fuzzer-4787296550256640

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
libavcodec/indeo4.c

index a3562f6..7dff9db 100644 (file)
@@ -260,12 +260,14 @@ static int decode_pic_hdr(IVI45DecContext *ctx, AVCodecContext *avctx)
  *  @param[in]     avctx     pointer to the AVCodecContext
  *  @return        result code: 0 = OK, negative number = error
  */
-static int decode_band_hdr(IVI45DecContext *ctx, IVIBandDesc *band,
+static int decode_band_hdr(IVI45DecContext *ctx, IVIBandDesc *arg_band,
                            AVCodecContext *avctx)
 {
     int plane, band_num, indx, transform_id, scan_indx;
     int i;
     int quant_mat;
+    IVIBandDesc temp_band, *band = &temp_band;
+    memcpy(&temp_band, arg_band, sizeof(temp_band));
 
     plane    = get_bits(&ctx->gb, 2);
     band_num = get_bits(&ctx->gb, 4);
@@ -395,10 +397,10 @@ static int decode_band_hdr(IVI45DecContext *ctx, IVIBandDesc *band,
 
         /* decode block huffman codebook */
         if (!get_bits1(&ctx->gb))
-            band->blk_vlc.tab = ctx->blk_vlc.tab;
+            arg_band->blk_vlc.tab = ctx->blk_vlc.tab;
         else
             if (ff_ivi_dec_huff_desc(&ctx->gb, 1, IVI_BLK_HUFF,
-                                     &band->blk_vlc, avctx))
+                                     &arg_band->blk_vlc, avctx))
                 return AVERROR_INVALIDDATA;
 
         /* select appropriate rvmap table for this band */
@@ -439,6 +441,9 @@ static int decode_band_hdr(IVI45DecContext *ctx, IVIBandDesc *band,
         return AVERROR_INVALIDDATA;
     }
 
+    band->blk_vlc = arg_band->blk_vlc;
+    memcpy(arg_band, band, sizeof(*arg_band));
+
     return 0;
 }