block: Limit request size (CVE-2014-0143)

Limiting the size of a single request to INT_MAX not only fixes a
direct integer overflow in bdrv_check_request() (which would only
trigger bad behaviour with ridiculously huge images, as in close to
2^64 bytes), but can also prevent overflows in all block drivers.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/block.c b/block.c
index acb70fd..7a90a1b 100644 (file)
--- a/block.c
+++ b/block.c
@@ -2588,6 +2588,10 @@ static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
 static int bdrv_check_request(BlockDriverState *bs, int64_t sector_num,
                               int nb_sectors)
 {
+    if (nb_sectors > INT_MAX / BDRV_SECTOR_SIZE) {
+        return -EIO;
+    }
+
     return bdrv_check_byte_request(bs, sector_num * BDRV_SECTOR_SIZE,
                                    nb_sectors * BDRV_SECTOR_SIZE);
 }