[Qemu-devel] [PATCH] Don't allow multiwrites against a block device without underlying medium

[Ryan Harper <ryanh@us.ibm.com>]

If the block device has been closed, we no longer have a medium to submit
IO against, check for this before submitting io.  This prevents a segfault
further in the code where we dereference elements of the block driver.

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
---
 block.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 92dd3fe..534e1bc 100644
--- a/block.c
+++ b/block.c
@@ -2407,6 +2407,11 @@ int bdrv_aio_multiwrite(BlockDriverState *bs, BlockRequest *reqs, int num_reqs)
         return 0;
     }
 
+    /* don't submit writes if we don't have a medium */
+    if (bs->drv == NULL) {
+       return -1;
+    }
+
     // Create MultiwriteCB structure
     mcb = qemu_mallocz(sizeof(*mcb) + num_reqs * sizeof(*mcb->callbacks));
     mcb->num_requests = 0;
-- 
1.7.1


-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com