avcodec/pngdec: Only allow one IHDR chunk

avcodec/pngdec: Only allow one IHDR chunk

Multiple IHDR chunks are forbidden in PNG
Fixes inconsistency and out of array accesses

Fixes: asan_heap-oob_4d5c5a_1738_cov_2638287726_c-m2-8f2b481b7fd9bd745e620b7c01a18df2.png
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Gbp-Pq: Name CVE-2015-6818.patch

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 58b57997ed6e92c55318d98640940ae2dda3529d..15114034fe652c539919271e83e6b8d5f0f534bf 100644 (file)
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -451,6 +451,11 @@ static int decode_frame(AVCodecContext *avctx,
                 goto fail;
             }
 
+            if (s->state & PNG_IHDR) {
+                av_log(avctx, AV_LOG_ERROR, "Multiple IHDR\n");
+                goto fail;
+            }
+
             s->width  = bytestream2_get_be32(&s->gb);
             s->height = bytestream2_get_be32(&s->gb);
             if (av_image_check_size(s->width, s->height, 0, avctx)) {