[FFmpeg-devel] [PATCH 1/4] avcodec/vp9_raw_reorder_bsf: Check for existence of data before reading it

[FFmpeg-devel] [PATCH 1/4] avcodec/vp9_raw_reorder_bsf: Check for existence of data before reading it

[Andreas Rheinhardt]

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
@michaelni: Please tell me the exact fuzzer issue id.

 libavcodec/vp9_raw_reorder_bsf.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/vp9_raw_reorder_bsf.c b/libavcodec/vp9_raw_reorder_bsf.c
index 6562399159..1608360fe1 100644
--- a/libavcodec/vp9_raw_reorder_bsf.c
+++ b/libavcodec/vp9_raw_reorder_bsf.c
@@ -292,6 +292,11 @@ static int vp9_raw_reorder_filter(AVBSFContext *bsf, AVPacket *out)
             return err;
         }
 
+        if (!in->size) {
+            av_packet_free(&in);
+            return AVERROR_INVALIDDATA;
+        }
+
         if ((in->data[in->size - 1] & 0xe0) == 0xc0) {
             av_log(bsf, AV_LOG_ERROR, "Input in superframes is not "
                    "supported.\n");
-- 
2.32.0

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[FFmpeg-devel] [PATCH 2/4] avcodec/vp9_superframe_bsf: Check for existence of data before reading it

[Andreas Rheinhardt]

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 <andreas.rheinhardt@outlook.com>
---
The current way of passthrough has been suggested by James.

 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 57681e29e4..df9b97fa3c 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);
-- 
2.32.0

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[FFmpeg-devel] [PATCH 3/4] avcodec/vp9_superframe_split_bsf: Discard invalid zero-sized frames

[Andreas Rheinhardt]

They are invalid in VP9. If any of the frames inside a superframe
had a size of zero, the code would either read into the next frame
or into the superframe index; so check for the length to stop this.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
Now split into a patch of its own.

 libavcodec/vp9_superframe_split_bsf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
index ed0444561a..7f0cad1ea0 100644
--- a/libavcodec/vp9_superframe_split_bsf.c
+++ b/libavcodec/vp9_superframe_split_bsf.c
@@ -70,7 +70,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
                         frame_size |= bytestream2_get_byte(&bc) << (j * 8);
 
                     total_size += frame_size;
-                    if (frame_size < 0 || total_size > in->size - idx_size) {
+                    if (frame_size <= 0 || total_size > in->size - idx_size) {
                         av_log(ctx, AV_LOG_ERROR,
                                "Invalid frame size in a superframe: %d\n", frame_size);
                         ret = AVERROR(EINVAL);
-- 
2.32.0

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[FFmpeg-devel] [PATCH 4/4] avcodec/vp9_superframe_split_bsf: Don't read inexistent data

[Andreas Rheinhardt]

Fixes: Out of array read
Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/vp9_superframe_split_bsf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
index 7f0cad1ea0..c9cf21b541 100644
--- a/libavcodec/vp9_superframe_split_bsf.c
+++ b/libavcodec/vp9_superframe_split_bsf.c
@@ -51,6 +51,9 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
             return ret;
         in = s->buffer_pkt;
 
+        if (!in->size)
+            goto passthrough;
+
         marker = in->data[in->size - 1];
         if ((marker & 0xe0) == 0xc0) {
             int length_size = 1 + ((marker >> 3) & 0x3);
@@ -121,6 +124,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
             out->pts = AV_NOPTS_VALUE;
 
     } else {
+passthrough:
         av_packet_move_ref(out, s->buffer_pkt);
     }
 
-- 
2.32.0

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