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avformat/webpenc: Fix memleak when using invalid packets

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The WebP muxer sometimes caches a packet it receives to write it later;
yet if a cached packet is too small (so small as to be invalid),
it is cached, but not written and not unreferenced. Such a packet leaks,
either by being overwritten by the next packet or because it is never
unreferenced at all.

Fix this by not caching unusable packets at all; and error out on
invalid packets.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2021-03-18 23:04:37 +01:00
parent 484a322f0a
commit f9043de99a
1 changed files with 11 additions and 10 deletions
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21
libavformat/webpenc.c
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@ -53,24 +53,22 @@ static int webp_init(AVFormatContext *s)
static int is_animated_webp_packet(AVPacket *pkt)
{
if (pkt->size) {
int skip = 0;
unsigned flags = 0;
if (pkt->size < 4)
return 0;
return AVERROR_INVALIDDATA;
if (AV_RL32(pkt->data) == AV_RL32("RIFF"))
skip = 12;
// Safe to do this as a valid WebP bitstream is >=30 bytes.
if (pkt->size < skip + 4)
return 0;
return AVERROR_INVALIDDATA;
if (AV_RL32(pkt->data + skip) == AV_RL32("VP8X")) {
flags |= pkt->data[skip + 4 + 4];
}
if (flags & 2) // ANIMATION_FLAG is on
return 1;
}
return 0;
}
@ -84,13 +82,9 @@ static int flush(AVFormatContext *s, int trailer, int64_t pts)
unsigned flags = 0;
int vp8x = 0;
if (w->last_pkt.size < 4)
return 0;
if (AV_RL32(w->last_pkt.data) == AV_RL32("RIFF"))
skip = 12;
if (w->last_pkt.size < skip + 4)
return 0; // Safe to do this as a valid WebP bitstream is >=30 bytes.
if (AV_RL32(w->last_pkt.data + skip) == AV_RL32("VP8X")) {
flags |= w->last_pkt.data[skip + 4 + 4];
vp8x = 1;
@ -149,7 +143,14 @@ static int flush(AVFormatContext *s, int trailer, int64_t pts)
static int webp_write_packet(AVFormatContext *s, AVPacket *pkt)
{
WebpContext *w = s->priv_data;
w->using_webp_anim_encoder |= is_animated_webp_packet(pkt);
int ret;
if (!pkt->size)
return 0;
ret = is_animated_webp_packet(pkt);
if (ret < 0)
return ret;
w->using_webp_anim_encoder |= ret;
if (w->using_webp_anim_encoder) {
avio_write(s->pb, pkt->data, pkt->size);