>>> On 01.03.13 at 18:33, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> If the frontend is using a non-native protocol (e.g., a 64-bit
> frontend with a 32-bit backend) and it sent an unrecognized request,
> the request was not translated and the response would have the
> incorrect ID. This may cause the frontend driver to behave
> incorrectly or crash.
>
> Since the ID field in the request is always in the same place,
> regardless of the request type we can get the correct ID and make a
> valid response (which will report BLKIF_RSP_EOPNOTSUPP).
>
> This bug affected 64-bit SLES 11 guests when using a 32-bit backend.
> This guest does a BLKIF_OP_RESERVED_1 (BLKIF_OP_PACKET in the SLES
> source) and would crash in blkif_int() as the ID in the response would
> be invalid.
I recognize the need for the change, and I'm also fine with the
patch, but ...
> --- a/include/xen/interface/io/blkif.h
> +++ b/include/xen/interface/io/blkif.h
> @@ -138,11 +138,21 @@ struct blkif_request_discard {
> uint8_t _pad3;
> } __attribute__((__packed__));
>
> +struct blkif_request_unknown {
> + uint8_t _pad1;
> + blkif_vdev_t _pad2; /* only for read/write requests */
> +#ifdef CONFIG_X86_64
> + uint32_t _pad3; /* offsetof(blkif_req..,u.unknown.id)==8*/
> +#endif
> + uint64_t id; /* private guest value, echoed in resp */
> +} __attribute__((__packed__));
> +
> struct blkif_request {
> uint8_t operation; /* BLKIF_OP_??? */
> union {
> struct blkif_request_rw rw;
> struct blkif_request_discard discard;
> + struct blkif_request_unknown unknown;
> } u;
> } __attribute__((__packed__));
>
... I wonder whether "unknown" here really is a suitable term.
I'd favor "generic" or "other", as "unknown" suggests we know
_nothing_ about it, which would include the position of the ID
field.
Also, we'd need a matching patch for the master copy of the
public header...
Jan
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html