1 files changed, 71 insertions, 10 deletions

diff --git a/block/cloop.c b/block/cloop.c
index b907023e10..b6ad50fbb4 100644
--- a/block/cloop.c
+++ b/block/cloop.c
@@ -26,6 +26,9 @@
 #include "qemu/module.h"
 #include <zlib.h>
 
+/* Maximum compressed block size */
+#define MAX_BLOCK_SIZE (64 * 1024 * 1024)
+
 typedef struct BDRVCloopState {
     CoMutex lock;
     uint32_t block_size;
@@ -68,6 +71,26 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
         return ret;
     }
     s->block_size = be32_to_cpu(s->block_size);
+    if (s->block_size % 512) {
+        error_setg(errp, "block_size %u must be a multiple of 512",
+                   s->block_size);
+        return -EINVAL;
+    }
+    if (s->block_size == 0) {
+        error_setg(errp, "block_size cannot be zero");
+        return -EINVAL;
+    }
+
+    /* cloop's create_compressed_fs.c warns about block sizes beyond 256 KB but
+     * we can accept more.  Prevent ridiculous values like 4 GB - 1 since we
+     * need a buffer this big.
+     */
+    if (s->block_size > MAX_BLOCK_SIZE) {
+        error_setg(errp, "block_size %u must be %u MB or less",
+                   s->block_size,
+                   MAX_BLOCK_SIZE / (1024 * 1024));
+        return -EINVAL;
+    }
 
     ret = bdrv_pread(bs->file, 128 + 4, &s->n_blocks, 4);
     if (ret < 0) {
@@ -76,7 +99,23 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
     s->n_blocks = be32_to_cpu(s->n_blocks);
 
     /* read offsets */
-    offsets_size = s->n_blocks * sizeof(uint64_t);
+    if (s->n_blocks > (UINT32_MAX - 1) / sizeof(uint64_t)) {
+        /* Prevent integer overflow */
+        error_setg(errp, "n_blocks %u must be %zu or less",
+                   s->n_blocks,
+                   (UINT32_MAX - 1) / sizeof(uint64_t));
+        return -EINVAL;
+    }
+    offsets_size = (s->n_blocks + 1) * sizeof(uint64_t);
+    if (offsets_size > 512 * 1024 * 1024) {
+        /* Prevent ridiculous offsets_size which causes memory allocation to
+         * fail or overflows bdrv_pread() size.  In practice the 512 MB
+         * offsets[] limit supports 16 TB images at 256 KB block size.
+         */
+        error_setg(errp, "image requires too many offsets, "
+                   "try increasing block size");
+        return -EINVAL;
+    }
     s->offsets = g_malloc(offsets_size);
 
     ret = bdrv_pread(bs->file, 128 + 4 + 4, s->offsets, offsets_size);
@@ -84,13 +123,37 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
-    for(i=0;i<s->n_blocks;i++) {
+    for (i = 0; i < s->n_blocks + 1; i++) {
+        uint64_t size;
+
         s->offsets[i] = be64_to_cpu(s->offsets[i]);
-        if (i > 0) {
-            uint32_t size = s->offsets[i] - s->offsets[i - 1];
-            if (size > max_compressed_block_size) {
-                max_compressed_block_size = size;
-            }
+        if (i == 0) {
+            continue;
+        }
+
+        if (s->offsets[i] < s->offsets[i - 1]) {
+            error_setg(errp, "offsets not monotonically increasing at "
+                       "index %u, image file is corrupt", i);
+            ret = -EINVAL;
+            goto fail;
+        }
+
+        size = s->offsets[i] - s->offsets[i - 1];
+
+        /* Compressed blocks should be smaller than the uncompressed block size
+         * but maybe compression performed poorly so the compressed block is
+         * actually bigger.  Clamp down on unrealistic values to prevent
+         * ridiculous s->compressed_block allocation.
+         */
+        if (size > 2 * MAX_BLOCK_SIZE) {
+            error_setg(errp, "invalid compressed block size at index %u, "
+                       "image file is corrupt", i);
+            ret = -EINVAL;
+            goto fail;
+        }
+
+        if (size > max_compressed_block_size) {
+            max_compressed_block_size = size;
         }
     }
 
@@ -180,9 +243,7 @@ static coroutine_fn int cloop_co_read(BlockDriverState *bs, int64_t sector_num,
 static void cloop_close(BlockDriverState *bs)
 {
     BDRVCloopState *s = bs->opaque;
-    if (s->n_blocks > 0) {
-        g_free(s->offsets);
-    }
+    g_free(s->offsets);
     g_free(s->compressed_block);
     g_free(s->uncompressed_block);
     inflateEnd(&s->zstream);