[FFmpeg-cvslog] avcodec/flac_parser: Do not lose header count in find_headers_search()

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Mon Feb  3 23:20:23 2020 +0100| [f9831156443a4ac8fb8e6d28c2ae673ec237cd5d] | committer: Michael Niedermayer

avcodec/flac_parser: Do not lose header count in find_headers_search()

Fixes: Timeout
Fixes: out of array access
Fixes: 20274/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FLAC_fuzzer-5649631988154368
Fixes: 19275/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FLAC_fuzzer-5757535722405888

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 55f9683cf6be97f4b398a7a35ee5bfd1208ac2a5)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f9831156443a4ac8fb8e6d28c2ae673ec237cd5d
---

 libavcodec/flac_parser.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/libavcodec/flac_parser.c b/libavcodec/flac_parser.c
index 00181f279a..ffa6a28457 100644
--- a/libavcodec/flac_parser.c
+++ b/libavcodec/flac_parser.c
@@ -216,16 +216,20 @@ static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size
     uint32_t x;
 
     for (i = 0; i < mod_offset; i++) {
-        if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
-            size = find_headers_search_validate(fpc, search_start + i);
+        if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8) {
+            int ret = find_headers_search_validate(fpc, search_start + i);
+            size = FFMAX(size, ret);
+        }
     }
 
     for (; i < buf_size - 1; i += 4) {
         x = AV_RB32(buf + i);
         if (((x & ~(x + 0x01010101)) & 0x80808080)) {
             for (j = 0; j < 4; j++) {
-                if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
-                    size = find_headers_search_validate(fpc, search_start + i + j);
+                if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8) {
+                    int ret = find_headers_search_validate(fpc, search_start + i + j);
+                    size = FFMAX(size, ret);
+                }
             }
         }
     }