[FFmpeg-cvslog] Check rangebits to avoid a possible crash.

[Frank Barchard]

ffmpeg | branch: release/0.6 | Frank Barchard <fbarchard at google.com> | Sat Jan 15 16:19:06 2011 +0000| [5e3d023702587c137ac0a725d601d26a8978a125] | committer: Janne Grunau

Check rangebits to avoid a possible crash.

Fixes issue 2548 (and Chrome issue 68115 and unknown CERT issues).

Patch by Frank Barchard, fbarchard at google

Originally committed as revision 26365 to svn://svn.ffmpeg.org/ffmpeg/trunk
(cherry picked from commit 13184036a6b1b1d4b61c91118c0896e9ad4634c3)

Signed-off-by: Janne Grunau <janne-ffmpeg at jannau.net>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=5e3d023702587c137ac0a725d601d26a8978a125
---

 libavcodec/vorbis_dec.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/libavcodec/vorbis_dec.c b/libavcodec/vorbis_dec.c
index a0f2342..f8067db 100644
--- a/libavcodec/vorbis_dec.c
+++ b/libavcodec/vorbis_dec.c
@@ -477,6 +477,7 @@ static int vorbis_parse_setup_hdr_floors(vorbis_context *vc)
         if (floor_setup->floor_type == 1) {
             uint_fast8_t  maximum_class = 0;
             uint_fast8_t  rangebits;
+            uint_fast32_t rangemax;
             uint_fast16_t floor1_values = 2;
 
             floor_setup->decode = vorbis_floor1_decode;
@@ -530,8 +531,15 @@ static int vorbis_parse_setup_hdr_floors(vorbis_context *vc)
 
 
             rangebits = get_bits(gb, 4);
+            rangemax = (1 << rangebits);
+            if (rangemax > vc->blocksize[1] / 2) {
+                av_log(vc->avccontext, AV_LOG_ERROR,
+                       "Floor value is too large for blocksize: %d (%d)\n",
+                       rangemax, vc->blocksize[1] / 2);
+                return -1;
+            }
             floor_setup->data.t1.list[0].x = 0;
-            floor_setup->data.t1.list[1].x = (1 << rangebits);
+            floor_setup->data.t1.list[1].x = rangemax;
 
             for (j = 0; j < floor_setup->data.t1.partitions; ++j) {
                 for (k = 0; k < floor_setup->data.t1.class_dimensions[floor_setup->data.t1.partition_class[j]]; ++k, ++floor1_values) {