[FFmpeg-cvslog] avformat/id3v2: Check the return from avio_get_str()

[Michael Niedermayer]

ffmpeg | branch: release/4.3 | Michael Niedermayer <michael at niedermayer.cc> | Sun Jan 31 16:14:03 2021 +0100| [499970980f88c62baf69feb060529d7a1534f25f] | committer: Michael Niedermayer

avformat/id3v2: Check the return from avio_get_str()

Fixes: out of array access
Fixes: 29446/clusterfuzz-testcase-minimized-ffmpeg_dem_AAC_fuzzer-5096222622875648

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 25f240fcb398eb499ca4b70c026a8bb9f2a32731)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=499970980f88c62baf69feb060529d7a1534f25f
---

 libavformat/id3v2.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
index 336a3964de..775fc0d514 100644
--- a/libavformat/id3v2.c
+++ b/libavformat/id3v2.c
@@ -605,7 +605,10 @@ static void read_apic(AVFormatContext *s, AVIOContext *pb, int taglen,
 
     /* mimetype */
     if (isv34) {
-        taglen -= avio_get_str(pb, taglen, mimetype, sizeof(mimetype));
+        int ret = avio_get_str(pb, taglen, mimetype, sizeof(mimetype));
+        if (ret < 0 || ret >= taglen)
+            goto fail;
+        taglen -= ret;
     } else {
         if (avio_read(pb, mimetype, 3) < 0)
             goto fail;