Fix potential OOB read with Error Concealment
This patch fixes an OOB read when error concealment is enabled and the
partition sizes are corrupt. The partition size read from the bitstream
was not being validated in EC mode.
Change-Id: Ia81dfd4bce1ab29ee78e42320abe52cee8318974
diff --git a/vp8/decoder/decodframe.c b/vp8/decoder/decodframe.c
index 9b35ffd..5ddf095 100644
--- a/vp8/decoder/decodframe.c
+++ b/vp8/decoder/decodframe.c
@@ -495,6 +495,15 @@
#endif
}
+
+static int read_is_valid(const unsigned char *start,
+ size_t len,
+ const unsigned char *end)
+{
+ return (start + len > start && start + len <= end);
+}
+
+
static void setup_token_decoder(VP8D_COMP *pbi,
const unsigned char *cx_data)
{
@@ -529,25 +538,41 @@
for (i = 0; i < num_part; i++)
{
const unsigned char *partition_size_ptr = cx_data + i * 3;
- ptrdiff_t partition_size;
+ ptrdiff_t partition_size, bytes_left;
+
+ bytes_left = user_data_end - partition;
/* Calculate the length of this partition. The last partition
- * size is implicit.
+ * size is implicit. If the partition size can't be read, then
+ * either use the remaining data in the buffer (for EC mode)
+ * or throw an error.
*/
if (i < num_part - 1)
{
- partition_size = read_partition_size(partition_size_ptr);
+ if (read_is_valid(partition_size_ptr, 3, user_data_end))
+ partition_size = read_partition_size(partition_size_ptr);
+ else if(pbi->ec_enabled)
+ partition_size = bytes_left;
+ else
+ vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
+ "Truncated partition size data");
}
else
- {
- partition_size = user_data_end - partition;
- }
+ partition_size = bytes_left;
- if (!pbi->ec_enabled && (partition + partition_size > user_data_end
- || partition + partition_size < partition))
- vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
- "Truncated packet or corrupt partition "
- "%d length", i + 1);
+ /* Validate the calculated partition length. If the buffer
+ * described by the partition can't be fully read, then restrict
+ * it to the portion that can be (for EC mode) or throw an error.
+ */
+ if (!read_is_valid(partition, partition_size, user_data_end))
+ {
+ if(pbi->ec_enabled)
+ partition_size = bytes_left;
+ else
+ vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
+ "Truncated packet or corrupt partition "
+ "%d length", i + 1);
+ }
if (vp8dx_start_decode(bool_decoder, partition, partition_size))
vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
