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

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 <[email protected]>
Reviewed-by: Max Reitz <[email protected]>
Signed-off-by: Stefan Hajnoczi <[email protected]>