From c12e8c97b13f33897bd9c6095432c9740504f5c7 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Wed, 27 May 2020 10:54:44 +0200 Subject: [PATCH] avcodec/vp9_superframe_bsf: Check for existence of data before reading it Packets without data need to be handled specially in order to avoid undefined reads. Pass these packets through unchanged in case there are no cached packets* and error out in case there are cached packets: Returning the packet would mess with the order of the packets; if one returned the zero-sized packet before the superframe that will be created from the packets in the cache, the zero-sized packet would overtake the packets in the cache; if one returned the packet later, the packets that complete the superframe will overtake the zero-sized packet. *: This case e.g. encompasses the scenario of updated extradata side-data at the end. Fixes: Out of array read Fixes: 45722/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_fuzzer-5173378975137792 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Andreas Rheinhardt --- libavcodec/vp9_superframe_bsf.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/libavcodec/vp9_superframe_bsf.c b/libavcodec/vp9_superframe_bsf.c index 349d43d62e..a0978c7ef0 100644 --- a/libavcodec/vp9_superframe_bsf.c +++ b/libavcodec/vp9_superframe_bsf.c @@ -108,6 +108,15 @@ static int vp9_superframe_filter(AVBSFContext *ctx, AVPacket *pkt) if (res < 0) return res; + if (!pkt->size) { + /* In case the cache is empty we can pass side-data-only packets + * through unchanged. Otherwise, such a packet makes no sense. */ + if (!s->n_cache) + return 0; + res = AVERROR_INVALIDDATA; + goto done; + } + marker = pkt->data[pkt->size - 1]; if ((marker & 0xe0) == 0xc0) { int nbytes = 1 + ((marker >> 3) & 0x3);