[patch 42/45] libata: fix off-by-one error in ata_tf_read_block()

[Greg KH <gregkh@suse.de>]

[-- Attachment #1: libata-fix-off-by-one-error-in-ata_tf_read_block.patch --]
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2.6.31-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
@@ -709,7 +709,13 @@ 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;