Patchwork [03/14] scsi: fix refcounting for reads

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Submitter Paolo Bonzini
Date May 4, 2012, 8:45 a.m.
Message ID <1336121154-26517-4-git-send-email-pbonzini@redhat.com>
Download mbox | patch
Permalink /patch/156837/
State New
Headers show

Comments

Paolo Bonzini - May 4, 2012, 8:45 a.m.
Recently introduced FUA support also gave us a use-after-free
of the BlockAcctCookie within a SCSIDiskReq, due to unbalanced
reference counting.

The patch fixes this by making scsi_do_read look like a combination
of scsi_*_complete + scsi_*_data.  It does both a ref (like
scsi_read_data) and an unref (like scsi_flush_complete).

Reported-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/scsi-disk.c |    7 +++++++
 1 file changed, 7 insertions(+)

Patch

diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index a029ab6..eca00a6 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -296,6 +296,13 @@  static void scsi_do_read(void *opaque, int ret)
         }
     }
 
+    if (r->req.io_canceled) {
+        return;
+    }
+
+    /* The request is used as the AIO opaque value, so add a ref.  */
+    scsi_req_ref(&r->req);
+
     if (r->req.sg) {
         dma_acct_start(s->qdev.conf.bs, &r->acct, r->req.sg, BDRV_ACCT_READ);
         r->req.resid -= r->req.sg->size;