Herbert Xu
2006-Oct-23 05:22 UTC
[Xen-devel] [BLOCK] blkback: Copy shared data before verification
Hi Keir:
This is a similar patch to the earlier ones for blktap/netback.
[BLOCK] blkback: Copy shared data before verification
As it is blkback verifies the metadata from the frontend in place.
This means we run the risk of the frontend changing the data after
we''ve verified it. This patch copies the data onto the stack before
verifying and using it to ensure we see a consistent snapshot.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Cheers,
--
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Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
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--
diff -r 8113c55a6efd linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c
--- a/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c Sun Oct 22 17:38:59
2006 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c Mon Oct 23 15:20:14
2006 +1000
@@ -293,7 +293,7 @@ static int do_block_io_op(blkif_t *blkif
static int do_block_io_op(blkif_t *blkif)
{
blkif_back_ring_t *blk_ring = &blkif->blk_ring;
- blkif_request_t *req;
+ blkif_request_t req;
pending_req_t *pending_req;
RING_IDX rc, rp;
int more_to_do = 0;
@@ -311,22 +311,22 @@ static int do_block_io_op(blkif_t *blkif
break;
}
- req = RING_GET_REQUEST(blk_ring, rc);
+ memcpy(&req, RING_GET_REQUEST(blk_ring, rc), sizeof(req));
blk_ring->req_cons = ++rc; /* before make_response() */
- switch (req->operation) {
+ switch (req.operation) {
case BLKIF_OP_READ:
blkif->st_rd_req++;
- dispatch_rw_block_io(blkif, req, pending_req);
+ dispatch_rw_block_io(blkif, &req, pending_req);
break;
case BLKIF_OP_WRITE:
blkif->st_wr_req++;
- dispatch_rw_block_io(blkif, req, pending_req);
+ dispatch_rw_block_io(blkif, &req, pending_req);
break;
default:
DPRINTK("error: unknown block io operation [%d]\n",
- req->operation);
- make_response(blkif, req->id, req->operation,
+ req.operation);
+ make_response(blkif, req.id, req.operation,
BLKIF_RSP_ERROR);
free_req(pending_req);
break;
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