From b97a4b658814b2de8b9f2a3bce491c002d34de31 Mon Sep 17 00:00:00 2001
From: Mark Thompson <sw@jkqxz.net>
Date: Sun, 2 Dec 2018 20:49:24 +0000
Subject: [PATCH] cbs_av1: Fix reading of overlong uvlc codes

The specification allows 2^32-1 to be encoded as any number of zeroes
greater than 31, followed by a one.  This previously failed because the
trace code would overflow the array containing the string representation
of the bits if there were more than 63 zeroes.  Fix that by splitting the
trace output into batches, and at the same time move it out of the default
path.

(While this seems likely to be a specification error, libaom does support
it so we probably should as well.)

From a test case by keval shah <skeval65@gmail.com>.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/cbs_av1.c | 58 ++++++++++++++++++++++++++++++--------------
 1 file changed, 40 insertions(+), 18 deletions(-)

diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
index b3f81ae93a534..f70ff1c94fcda 100644
--- a/libavcodec/cbs_av1.c
+++ b/libavcodec/cbs_av1.c
@@ -29,45 +29,67 @@ static int cbs_av1_read_uvlc(CodedBitstreamContext *ctx, GetBitContext *gbc,
                              const char *name, uint32_t *write_to,
                              uint32_t range_min, uint32_t range_max)
 {
-    uint32_t value;
-    int position, zeroes, i, j;
-    char bits[65];
+    uint32_t zeroes, bits_value, value;
+    int position;
 
     if (ctx->trace_enable)
         position = get_bits_count(gbc);
 
-    zeroes = i = 0;
+    zeroes = 0;
     while (1) {
-        if (get_bits_left(gbc) < zeroes + 1) {
+        if (get_bits_left(gbc) < 1) {
             av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid uvlc code at "
                    "%s: bitstream ended.\n", name);
             return AVERROR_INVALIDDATA;
         }
 
-        if (get_bits1(gbc)) {
-            bits[i++] = '1';
+        if (get_bits1(gbc))
             break;
-        } else {
-            bits[i++] = '0';
-            ++zeroes;
-        }
+        ++zeroes;
     }
 
     if (zeroes >= 32) {
         value = MAX_UINT_BITS(32);
     } else {
-        value = get_bits_long(gbc, zeroes);
-
-        for (j = 0; j < zeroes; j++)
-            bits[i++] = (value >> (zeroes - j - 1) & 1) ? '1' : '0';
+        if (get_bits_left(gbc) < zeroes) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid uvlc code at "
+                   "%s: bitstream ended.\n", name);
+            return AVERROR_INVALIDDATA;
+        }
 
-        value += (1 << zeroes) - 1;
+        bits_value = get_bits_long(gbc, zeroes);
+        value = bits_value + (UINT32_C(1) << zeroes) - 1;
     }
 
     if (ctx->trace_enable) {
+        char bits[65];
+        int i, j, k;
+
+        if (zeroes >= 32) {
+            while (zeroes > 32) {
+                k = FFMIN(zeroes - 32, 32);
+                for (i = 0; i < k; i++)
+                    bits[i] = '0';
+                bits[i] = 0;
+                ff_cbs_trace_syntax_element(ctx, position, name,
+                                            NULL, bits, 0);
+                zeroes -= k;
+                position += k;
+            }
+        }
+
+        for (i = 0; i < zeroes; i++)
+            bits[i] = '0';
+        bits[i++] = '1';
+
+        if (zeroes < 32) {
+            for (j = 0; j < zeroes; j++)
+                bits[i++] = (bits_value >> (zeroes - j - 1) & 1) ? '1' : '0';
+        }
+
         bits[i] = 0;
-        ff_cbs_trace_syntax_element(ctx, position, name, NULL,
-                                    bits, value);
+        ff_cbs_trace_syntax_element(ctx, position, name,
+                                    NULL, bits, value);
     }
 
     if (value < range_min || value > range_max) {