avcodec/ffv1enc: Use dummies to avoid UB pointer arithmetic

Fixes the following FATE-tests when run under Clang-UBSan: ffmpeg-loopback-decoding, lavf-mxf_ffv1, vsynth{1,2,3,_lena}-ffv1-v{0,2}, vsynth1-ffv{1,2,3,_lena}, vsynth{1,2,3,_lena}-ffv1-v3-yuv{420p,422p10,444p16}

Andreas Rheinhardt committed 1 year ago

Commit bdb4cd41 parent 134c1d82 files · +9 −1Browse files

Showing the changes to libavcodec (2 of 2 files). Show all

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2 files

libavcodec/ffv1enc.c +5 −0
libavcodec/ffv1enc_template.c +4 −1

libavcodec/ffv1enc.c+5−0

     int16_t *sample[3];
     sc->run_index = 0;
+    sample[2] = sc->sample_buffer; // dummy to avoid UB pointer arithmetic
     memset(sc->sample_buffer, 0, ring_size * (w + 6) * sizeof(*sc->sample_buffer));
     for (y = 0; y < h; y++) {
     sc->run_index = 0;
+    for (int p = 0; p < MAX_PLANES; ++p)
+        sample[p][2] = sc->sample_buffer32; // dummy to avoid UB pointer arithmetic
     memset(RENAME(sc->sample_buffer), 0, ring_size * MAX_PLANES *
            (w + 6) * sizeof(*RENAME(sc->sample_buffer)));

libavcodec/ffv1enc_template.c+4−1

 static av_always_inline int
 RENAME(encode_line)(FFV1Context *f, FFV1SliceContext *sc,
                     void *logctx,
-                    int w, TYPE *sample[3], int plane_index, int bits,
+                    int w, TYPE *const sample[3], int plane_index, int bits,
                     int ac, int pass1)
 {
     PlaneContext *const p = &sc->plane[plane_index];
     sc->run_index = 0;
+    for (int p = 0; p < MAX_PLANES; ++p)
+        sample[p][2] = RENAME(sc->sample_buffer);
     memset(RENAME(sc->sample_buffer), 0, ring_size * MAX_PLANES *
            (w + 6) * sizeof(*RENAME(sc->sample_buffer)));

avcodec/ffv1enc: Use dummies to avoid UB pointer arithmetic

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