[FFmpeg-cvslog] avcodec/g2meet: Replace fake allocation avoidance for framebuf

[Michael Niedermayer]

ffmpeg | branch: release/4.2 | Michael Niedermayer <michael at niedermayer.cc> | Tue Jan 24 22:48:46 2023 +0100| [a2d1a8c78bb9f0d8d1e2f6e5c31b5ed7eece16f0] | committer: Michael Niedermayer

avcodec/g2meet: Replace fake allocation avoidance for framebuf

framebuf is only allocated when the new width/height are larger than the old
but nothing sets the old so its always allocated.
Use av_fast_mallocz() instead.

Fixes: Timeout
Fixes: 55094/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_G2M_fuzzer-5116909932904448

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 38adbc6eebd7f2f34ecf1b0b18019e88bad9d9f4)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a2d1a8c78bb9f0d8d1e2f6e5c31b5ed7eece16f0
---

 libavcodec/g2meet.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/libavcodec/g2meet.c b/libavcodec/g2meet.c
index 7ef275c9fe..5856d51783 100644
--- a/libavcodec/g2meet.c
+++ b/libavcodec/g2meet.c
@@ -143,7 +143,8 @@ typedef struct G2MContext {
     int        got_header;
 
     uint8_t    *framebuf;
-    int        framebuf_stride, old_width, old_height;
+    int        framebuf_stride;
+    unsigned int framebuf_allocated;
 
     uint8_t    *synth_tile, *jpeg_tile, *epic_buf, *epic_buf_base;
     int        tile_stride, epic_buf_stride, old_tile_w, old_tile_h;
@@ -1179,14 +1180,13 @@ static int g2m_init_buffers(G2MContext *c)
 {
     int aligned_height;
 
-    if (!c->framebuf || c->old_width < c->width || c->old_height < c->height) {
-        c->framebuf_stride = FFALIGN(c->width + 15, 16) * 3;
-        aligned_height     = c->height + 15;
-        av_free(c->framebuf);
-        c->framebuf = av_mallocz_array(c->framebuf_stride, aligned_height);
-        if (!c->framebuf)
-            return AVERROR(ENOMEM);
-    }
+    c->framebuf_stride = FFALIGN(c->width + 15, 16) * 3;
+    aligned_height = c->height + 15;
+
+    av_fast_mallocz(&c->framebuf, &c->framebuf_allocated, c->framebuf_stride * aligned_height);
+    if (!c->framebuf)
+        return AVERROR(ENOMEM);
+
     if (!c->synth_tile || !c->jpeg_tile ||
         (c->compression == 2 && !c->epic_buf_base) ||
         c->old_tile_w < c->tile_width ||
@@ -1638,6 +1638,7 @@ static av_cold int g2m_decode_end(AVCodecContext *avctx)
     av_freep(&c->jpeg_tile);
     av_freep(&c->cursor);
     av_freep(&c->framebuf);
+    c->framebuf_allocated = 0;
 
     return 0;
 }