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From 2fd88dcb7fdb90508a85c30a32516ff57f081cba Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Wed, 5 Sep 2012 17:54:36 +0200
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Subject: [PATCH] scsi-disk: fix check for out-of-range LBA
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This fix is needed to correctly handle 0-block read and writes.
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Without it, a 0-block access at LBA 0 would underflow.
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 12ca76fc48081b3a0ad1a70546abfcf198aedfc4)
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Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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---
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hw/scsi-disk.c | 6 +++++-
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1 file changed, 5 insertions(+), 1 deletion(-)
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diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
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index 3959603..d621852 100644
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--- a/hw/scsi-disk.c
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+++ b/hw/scsi-disk.c
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@@ -1456,9 +1456,13 @@ static inline bool check_lba_range(SCSIDiskState *s,
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* The first line tests that no overflow happens when computing the last
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* sector. The second line tests that the last accessed sector is in
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* range.
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+ *
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+ * Careful, the computations should not underflow for nb_sectors == 0,
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+ * and a 0-block read to the first LBA beyond the end of device is
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+ * valid.
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*/
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return (sector_num <= sector_num + nb_sectors &&
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- sector_num + nb_sectors - 1 <= s->qdev.max_lba);
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+ sector_num + nb_sectors <= s->qdev.max_lba + 1);
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}
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typedef struct UnmapCBData {
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--
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1.7.12.1
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