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Subject[PATCH #upstream-fixes] libata: fix off-by-one error in ata_tf_read_block()
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>
---
> Well, I expect fix by you (or other libata hackers) since I think you
> can write better warning message and changelog than me ;)

In that case, sure. Thanks a lot for the nice spotting. :-)

drivers/ata/libata-core.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 072ba5e..e71149b 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -709,7 +709,13 @@ u64 ata_tf_read_block(struct ata_taskfile *tf, struct ata_device *dev)
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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