From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Wed, 26 Mar 2014 13:05:26 +0100
Subject: [PATCH] block/cloop: prevent offsets_size integer overflow
 (CVE-2014-0143)

The following integer overflow in offsets_size can lead to out-of-bounds
memory stores when n_blocks has a huge value:

    uint32_t n_blocks, offsets_size;
    [...]
    ret = bdrv_pread(bs->file, 128 + 4, &s->n_blocks, 4);
    [...]
    s->n_blocks = be32_to_cpu(s->n_blocks);

    /* read offsets */
    offsets_size = s->n_blocks * sizeof(uint64_t);
    s->offsets = g_malloc(offsets_size);

    [...]

    for(i=0;i<s->n_blocks;i++) {
        s->offsets[i] = be64_to_cpu(s->offsets[i]);

offsets_size can be smaller than n_blocks due to integer overflow.
Therefore s->offsets[] is too small when the for loop byteswaps offsets.

This patch refuses to open files if offsets_size would overflow.

Note that changing the type of offsets_size is not a fix since 32-bit
hosts still only have 32-bit size_t.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 509a41bab5306181044b5fff02eadf96d9c8676a)

Conflicts:
	tests/qemu-iotests/075
	tests/qemu-iotests/075.out
---
 block/cloop.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/cloop.c b/block/cloop.c
index c2441b0..e20d0d8 100644
--- a/block/cloop.c
+++ b/block/cloop.c
@@ -98,6 +98,13 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags)
     s->n_blocks = be32_to_cpu(s->n_blocks);
 
     /* read offsets */
+    if (s->n_blocks > UINT32_MAX / sizeof(uint64_t)) {
+        /* Prevent integer overflow */
+        fprintf(stderr, "n_blocks %u must be %zu or less",
+                   s->n_blocks,
+                   UINT32_MAX / sizeof(uint64_t));
+        return -EINVAL;
+    }
     offsets_size = s->n_blocks * sizeof(uint64_t);
     s->offsets = g_malloc(offsets_size);