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scsi: fix refcounting for reads 

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>
This commit is contained in:
Paolo Bonzini 2012-04-24 08:41:04 +02:00
parent 12a08998fe
commit 31e8fd86f2
1 changed files with 7 additions and 0 deletions
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7
hw/scsi-disk.c
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@ -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;