ref: cdae03a4eb9690df77b5926a7835b2d355c62a13
parent: e28e08146e468c55e435d19b2c95654e04fe3044
author: John Koleszar <jkoleszar@google.com>
date: Fri Aug 5 08:27:25 EDT 2011
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
--- 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 = bytes_left;
+
+ /* 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))
{- partition_size = user_data_end - partition;
+ 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 (!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);
if (vp8dx_start_decode(bool_decoder, partition, partition_size))
vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,