[PULL 3/3] virtio-blk: fix out-of-bounds access to bitmap in notify_guest_bh

[Stefan Hajnoczi <stefanha@xxxxxxxxxx>]

From: Li Hangjing <lihangjing@xxxxxxxxx>

When the number of a virtio-blk device's virtqueues is larger than
BITS_PER_LONG, the out-of-bounds access to bitmap[ ] will occur.

Fixes: e21737ab15 ("virtio-blk: multiqueue batch notify")
Cc: qemu-stable@xxxxxxxxxx
Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Signed-off-by: Li Hangjing <lihangjing@xxxxxxxxx>
Reviewed-by: Xie Yongji <xieyongji@xxxxxxxxx>
Reviewed-by: Chai Wen <chaiwen@xxxxxxxxx>
Message-id: 20191216023050.48620-1-lihangjing@xxxxxxxxx
Message-Id: <20191216023050.48620-1-lihangjing@xxxxxxxxx>
Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
---
 hw/block/dataplane/virtio-blk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 119906a5fe..1b52e8159c 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -67,7 +67,7 @@ static void notify_guest_bh(void *opaque)
     memset(s->batch_notify_vqs, 0, sizeof(bitmap));
 
     for (j = 0; j < nvqs; j += BITS_PER_LONG) {
-        unsigned long bits = bitmap[j];
+        unsigned long bits = bitmap[j / BITS_PER_LONG];
 
         while (bits != 0) {
             unsigned i = j + ctzl(bits);
-- 
2.23.0

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