From 2fd88dcb7fdb90508a85c30a32516ff57f081cba Mon Sep 17 00:00:00 2001 From: Paolo Bonzini 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 (cherry picked from commit 12ca76fc48081b3a0ad1a70546abfcf198aedfc4) Signed-off-by: Michael Roth --- 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 { -- 1.7.12.1