[Bf-blender-cvs] [0ac83d05d7c] blender-v2.83-release: Fix T94661: Out-of-bounds memory access due to malformed DDS image file

[Sergey Sharybin]

Commit: 0ac83d05d7cccec436bb939e0aa768f6a3d77d72
Author: Sergey Sharybin
Date:   Mon Jan 10 14:26:57 2022 +0100
Branches: blender-v2.83-release
https://developer.blender.org/rB0ac83d05d7cccec436bb939e0aa768f6a3d77d72

Fix T94661: Out-of-bounds memory access due to malformed DDS image file

Harden bounds check in the stream reader avoiding integer overflow.

===================================================================

M	source/blender/imbuf/intern/dds/Stream.cpp

===================================================================

diff --git a/source/blender/imbuf/intern/dds/Stream.cpp b/source/blender/imbuf/intern/dds/Stream.cpp
index 271717f165c..a0a5a75ef8d 100644
--- a/source/blender/imbuf/intern/dds/Stream.cpp
+++ b/source/blender/imbuf/intern/dds/Stream.cpp
@@ -26,6 +26,21 @@
 static const char *msg_error_seek = "DDS: trying to seek beyond end of stream (corrupt file?)";
 static const char *msg_error_read = "DDS: trying to read beyond end of stream (corrupt file?)";
 
+inline bool is_read_within_bounds(const Stream &mem, unsigned int cnt)
+{
+  if (mem.pos >= mem.size) {
+    /* No more data remained in the memory buffer. */
+    return false;
+  }
+
+  if (cnt > mem.size - mem.pos) {
+    /* Reading past the memory bounds. */
+    return false;
+  }
+
+  return true;
+}
+
 unsigned int Stream::seek(unsigned int p)
 {
   if (p > size) {
@@ -40,7 +55,7 @@ unsigned int Stream::seek(unsigned int p)
 
 unsigned int mem_read(Stream &mem, unsigned long long &i)
 {
-  if (mem.pos + 8 > mem.size) {
+  if (!is_read_within_bounds(mem, 8)) {
     mem.set_failed(msg_error_seek);
     return (0);
   }
@@ -51,7 +66,7 @@ unsigned int mem_read(Stream &mem, unsigned long long &i)
 
 unsigned int mem_read(Stream &mem, unsigned int &i)
 {
-  if (mem.pos + 4 > mem.size) {
+  if (!is_read_within_bounds(mem, 4)) {
     mem.set_failed(msg_error_read);
     return (0);
   }
@@ -62,7 +77,7 @@ unsigned int mem_read(Stream &mem, unsigned int &i)
 
 unsigned int mem_read(Stream &mem, unsigned short &i)
 {
-  if (mem.pos + 2 > mem.size) {
+  if (!is_read_within_bounds(mem, 2)) {
     mem.set_failed(msg_error_read);
     return (0);
   }
@@ -73,7 +88,7 @@ unsigned int mem_read(Stream &mem, unsigned short &i)
 
 unsigned int mem_read(Stream &mem, unsigned char &i)
 {
-  if (mem.pos + 1 > mem.size) {
+  if (!is_read_within_bounds(mem, 1)) {
     mem.set_failed(msg_error_read);
     return (0);
   }
@@ -84,7 +99,7 @@ unsigned int mem_read(Stream &mem, unsigned char &i)
 
 unsigned int mem_read(Stream &mem, unsigned char *i, unsigned int cnt)
 {
-  if (mem.pos + cnt > mem.size) {
+  if (!is_read_within_bounds(mem, cnt)) {
     mem.set_failed(msg_error_read);
     return (0);
   }