From: John Koleszar <jkoleszar@google.com>
Date: Thu, 4 Nov 2010 20:59:26 +0000 (-0400)
Subject: fix integer promotion bug in partition size check
X-Git-Url: https://review.webmproject.org/gitweb?p=libvpx.git;a=commitdiff_plain;h=9fb80f7170ec48e23c3c7b477149eeb37081c699;hp=09bcc1f710ea65dc158639479288fb1908ff0c53

fix integer promotion bug in partition size check

The check '(user_data_end - partition < partition_size)' must be
evaluated as a signed comparison, but because partition_size was
unsigned, the LHS was promoted to unsigned, causing an incorrect
result on 32-bit. Instead, check the upper and lower bounds of
the segment separately.

Change-Id: I6266aba7fd7de084268712a3d2a81424ead7aa06
---

diff --git a/vp8/decoder/decodframe.c b/vp8/decoder/decodframe.c
index 2d81d61..f5e49a1 100644
--- a/vp8/decoder/decodframe.c
+++ b/vp8/decoder/decodframe.c
@@ -462,7 +462,8 @@ static void setup_token_decoder(VP8D_COMP *pbi,
             partition_size = user_data_end - partition;
         }
 
-        if (user_data_end - partition < partition_size)
+        if (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);
@@ -580,7 +581,8 @@ int vp8_decode_frame(VP8D_COMP *pbi)
         (data[0] | (data[1] << 8) | (data[2] << 16)) >> 5;
     data += 3;
 
-    if (data_end - data < first_partition_length_in_bytes)
+    if (data + first_partition_length_in_bytes > data_end
+        || data + first_partition_length_in_bytes < data)
         vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                            "Truncated packet or corrupt partition 0 length");
     vp8_setup_version(pc);
diff --git a/vp8/vp8_dx_iface.c b/vp8/vp8_dx_iface.c
index e7e5356..f0adf5b 100644
--- a/vp8/vp8_dx_iface.c
+++ b/vp8/vp8_dx_iface.c
@@ -253,8 +253,11 @@ static vpx_codec_err_t vp8_peek_si(const uint8_t         *data,
                                    unsigned int           data_sz,
                                    vpx_codec_stream_info_t *si)
 {
-
     vpx_codec_err_t res = VPX_CODEC_OK;
+
+    if(data + data_sz <= data)
+        res = VPX_CODEC_INVALID_PARAM;
+    else
     {
         /* Parse uncompresssed part of key frame header.
          * 3 bytes:- including version, frame type and an offset
@@ -331,7 +334,10 @@ static vpx_codec_err_t vp8_decode(vpx_codec_alg_priv_t  *ctx,
 
     ctx->img_avail = 0;
 
-    /* Determine the stream parameters */
+    /* Determine the stream parameters. Note that we rely on peek_si to
+     * validate that we have a buffer that does not wrap around the top
+     * of the heap.
+     */
     if (!ctx->si.h)
         res = ctx->base.iface->dec.peek_si(data, data_sz, &ctx->si);