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Subject[patch 06/10] libata: fix off-by-one error in ata_tf_read_block()
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Tejun Heo <htejun@gmail.com>
commit ac8672ea922bde59acf50eaa1eaa1640a6395fd2 upstream.

ata_tf_read_block() has off-by-one error when converting CHS address
to LBA. The bug isn't very visible because ata_tf_read_block() is
used only when generating sense data for a failed RW command and CHS
addressing isn't used too often these days.

This problem was spotted by Atsushi Nemoto.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/ata/libata-core.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -565,7 +565,13 @@ u64 ata_tf_read_block(struct ata_taskfil
head = tf->device & 0xf;
sect = tf->lbal;

- block = (cyl * dev->heads + head) * dev->sectors + sect;
+ if (!sect) {
+ ata_dev_printk(dev, KERN_WARNING, "device reported "
+ "invalid CHS sector 0\n");
+ sect = 1; /* oh well */
+ }
+
+ block = (cyl * dev->heads + head) * dev->sectors + sect - 1;
}

return block;



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