qemu/0214-scsi-disk-fix-check-for-out-of-range-LBA.patch

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2012-10-28 18:05:07 +00:00
From 2fd88dcb7fdb90508a85c30a32516ff57f081cba Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 5 Sep 2012 17:54:36 +0200
Subject: [PATCH] scsi-disk: fix check for out-of-range LBA
This fix is needed to correctly handle 0-block read and writes.
Without it, a 0-block access at LBA 0 would underflow.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 12ca76fc48081b3a0ad1a70546abfcf198aedfc4)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
hw/scsi-disk.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 3959603..d621852 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -1456,9 +1456,13 @@ static inline bool check_lba_range(SCSIDiskState *s,
* The first line tests that no overflow happens when computing the last
* sector. The second line tests that the last accessed sector is in
* range.
+ *
+ * Careful, the computations should not underflow for nb_sectors == 0,
+ * and a 0-block read to the first LBA beyond the end of device is
+ * valid.
*/
return (sector_num <= sector_num + nb_sectors &&
- sector_num + nb_sectors - 1 <= s->qdev.max_lba);
+ sector_num + nb_sectors <= s->qdev.max_lba + 1);
}
typedef struct UnmapCBData {