[FFmpeg-cvslog] avcodec/exr: Check buf_size more completely

[Michael Niedermayer]

ffmpeg | branch: release/3.2 | Michael Niedermayer <michael at niedermayer.cc> | Fri Dec 29 03:00:19 2017 +0100| [439f3564fa548f5d7385220af29bac44d3e8ff35] | committer: Michael Niedermayer

avcodec/exr: Check buf_size more completely

Fixes: Out of heap array read
Fixes: 4683/clusterfuzz-testcase-minimized-6152313673613312

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 903be5e4f66268273dc6e3c42a7fdeaab32066ef)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=439f3564fa548f5d7385220af29bac44d3e8ff35
---

 libavcodec/exr.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libavcodec/exr.c b/libavcodec/exr.c
index 4b0cf21cdb..c7b138e297 100644
--- a/libavcodec/exr.c
+++ b/libavcodec/exr.c
@@ -1044,7 +1044,7 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
     line_offset = AV_RL64(s->gb.buffer + jobnr * 8);
 
     if (s->is_tile) {
-        if (line_offset > buf_size - 20)
+        if (buf_size < 20 || line_offset > buf_size - 20)
             return AVERROR_INVALIDDATA;
 
         src  = buf + line_offset + 20;
@@ -1055,7 +1055,7 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
         tileLevelY = AV_RL32(src - 8);
 
         data_size = AV_RL32(src - 4);
-        if (data_size <= 0 || data_size > buf_size)
+        if (data_size <= 0 || data_size > buf_size - line_offset - 20)
             return AVERROR_INVALIDDATA;
 
         if (tileLevelX || tileLevelY) { /* tile level, is not the full res level */
@@ -1088,7 +1088,7 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
         td->channel_line_size = td->xsize * s->current_channel_offset;/* uncompress size of one line */
         uncompressed_size = td->channel_line_size * (uint64_t)td->ysize;/* uncompress size of the block */
     } else {
-        if (line_offset > buf_size - 8)
+        if (buf_size < 8 || line_offset > buf_size - 8)
             return AVERROR_INVALIDDATA;
 
         src  = buf + line_offset + 8;
@@ -1098,7 +1098,7 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
             return AVERROR_INVALIDDATA;
 
         data_size = AV_RL32(src - 4);
-        if (data_size <= 0 || data_size > buf_size)
+        if (data_size <= 0 || data_size > buf_size - line_offset - 8)
             return AVERROR_INVALIDDATA;
 
         td->ysize          = FFMIN(s->scan_lines_per_block, s->ymax - line + 1); /* s->ydelta - line ?? */