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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>
This commit is contained in:
Paolo Bonzini 2012-09-05 17:54:36 +02:00
parent 444bc90861
commit 12ca76fc48
1 changed files with 5 additions and 1 deletions
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6
hw/scsi-disk.c
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@ -1456,9 +1456,13 @@ static inline bool check_lba_range(SCSIDiskState *s,
* The first line tests that no overflow happens when computing the last * The first line tests that no overflow happens when computing the last
* sector. The second line tests that the last accessed sector is in * sector. The second line tests that the last accessed sector is in
* range. * 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 && 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 { typedef struct UnmapCBData {