Fix buffer overflow vulernability in thumbnail file reading.

Fixes CVE-2017-2908 from T52924.

Differential Revision: https://developer.blender.org/D3001

source/blender/blenkernel/BKE_main.h

@@ -145,7 +145,8 @@ typedef struct Main {
 
 #define BLEN_THUMB_SIZE 128
 
-#define BLEN_THUMB_MEMSIZE(_x, _y) (sizeof(BlendThumbnail) + (size_t)((_x) * (_y)) * sizeof(int))
+#define BLEN_THUMB_MEMSIZE(_x, _y) (sizeof(BlendThumbnail) + ((size_t)(_x) * (size_t)(_y)) * sizeof(int))
+#define BLEN_THUMB_SAFE_MEMSIZE(_x, _y) ((uint64_t)_x * (uint64_t)_y < (SIZE_MAX / (sizeof(int) * 4)))
 
 #ifdef __cplusplus
 }

source/blender/blenloader/BLO_blend_defs.h

@@ -75,6 +75,6 @@ enum {
 	ENDB = BLEND_MAKE_ID('E', 'N', 'D', 'B'),
 };
 
-#define BLEN_THUMB_MEMSIZE_FILE(_x, _y) (sizeof(int) * (size_t)(2 + (_x) * (_y)))
+#define BLEN_THUMB_MEMSIZE_FILE(_x, _y) (sizeof(int) * (2 + (size_t)(_x) * (size_t)(_y)))
 
 #endif  /* __BLO_BLEND_DEFS_H__ */

source/blender/blenloader/intern/readfile.c

@@ -982,7 +982,13 @@ static int *read_file_thumbnail(FileData *fd)
 				BLI_endian_switch_int32(&data[1]);
 			}
 
-			if (bhead->len < BLEN_THUMB_MEMSIZE_FILE(data[0], data[1])) {
+			int width = data[0];
+			int height = data[1];
+
+			if (!BLEN_THUMB_SAFE_MEMSIZE(width, height)) {
+				break;
+			}
+			if (bhead->len < BLEN_THUMB_MEMSIZE_FILE(width, height)) {
 				break;
 			}
 
@@ -1421,23 +1427,28 @@ bool BLO_library_path_explode(const char *path, char *r_dir, char **r_group, cha
 BlendThumbnail *BLO_thumbnail_from_file(const char *filepath)
 {
 	FileData *fd;
-	BlendThumbnail *data;
+	BlendThumbnail *data = NULL;
 	int *fd_data;
 
 	fd = blo_openblenderfile_minimal(filepath);
 	fd_data = fd ? read_file_thumbnail(fd) : NULL;
 
 	if (fd_data) {
-		const size_t sz = BLEN_THUMB_MEMSIZE(fd_data[0], fd_data[1]);
+		int width = fd_data[0];
+		int height = fd_data[1];
+
+		/* Protect against buffer overflow vulnerability. */
+		if (BLEN_THUMB_SAFE_MEMSIZE(width, height)) {
+			const size_t sz = BLEN_THUMB_MEMSIZE(width, height);
 			data = MEM_mallocN(sz, __func__);
 
-		BLI_assert((sz - sizeof(*data)) == (BLEN_THUMB_MEMSIZE_FILE(fd_data[0], fd_data[1]) - (sizeof(*fd_data) * 2)));
+			if (data) {
-		data->width = fd_data[0];
+				BLI_assert((sz - sizeof(*data)) == (BLEN_THUMB_MEMSIZE_FILE(width, height) - (sizeof(*fd_data) * 2)));
-		data->height = fd_data[1];
+				data->width = width;
+				data->height = height;
 				memcpy(data->rect, &fd_data[2], sz - sizeof(*data));
 			}
-	else {
+		}
-		data = NULL;
 	}
 
 	blo_freefiledata(fd);
@@ -8624,16 +8635,22 @@ BlendFileData *blo_read_file_internal(FileData *fd, const char *filepath)
 		const int *data = read_file_thumbnail(fd);
 
 		if (data) {
-			const size_t sz = BLEN_THUMB_MEMSIZE(data[0], data[1]);
+			int width = data[0];
+			int height = data[1];
+
+			/* Protect against buffer overflow vulnerability. */
+			if (BLEN_THUMB_SAFE_MEMSIZE(width, height)) {
+				const size_t sz = BLEN_THUMB_MEMSIZE(width, height);
 				bfd->main->blen_thumb = MEM_mallocN(sz, __func__);
 
 				BLI_assert((sz - sizeof(*bfd->main->blen_thumb)) ==
-			           (BLEN_THUMB_MEMSIZE_FILE(data[0], data[1]) - (sizeof(*data) * 2)));
+				           (BLEN_THUMB_MEMSIZE_FILE(width, height) - (sizeof(*data) * 2)));
-			bfd->main->blen_thumb->width = data[0];
+				bfd->main->blen_thumb->width = width;
-			bfd->main->blen_thumb->height = data[1];
+				bfd->main->blen_thumb->height = height;
 				memcpy(bfd->main->blen_thumb->rect, &data[2], sz - sizeof(*bfd->main->blen_thumb));
 			}
 		}
+	}
 
 	while (bhead) {
 		switch (bhead->code) {

source/blender/makesdna/intern/dna_genfile.c

@@ -173,7 +173,9 @@ void DNA_sdna_free(SDNA *sdna)
 	MEM_freeN(sdna->structs);
 
 #ifdef WITH_DNA_GHASH
+	if (sdna->structs_map) {
 		BLI_ghash_free(sdna->structs_map, NULL, NULL);
+	}
 #endif
 
 	MEM_freeN(sdna);