linux-kernel - [PATCH] libata: Avoid overflow in ata_tf_to_lba48() when tf->hba

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Message-ID: <ada4p2wmg5n.fsf_-_@cisco.com>
Date:	Tue, 28 Oct 2008 16:52:20 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	"Phillip O'Donnell" <phillip.odonnell@...il.com>, jeff@...zik.org
Cc:	"Oskar Liljeblad" <oskar@....mine.nu>, jeff@...zik.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] libata: Avoid overflow in ata_tf_to_lba48() when tf->hba_lbal > 127

In ata_tf_to_lba48(), when evaluating

	(tf->hob_lbal & 0xff) << 24

the expression is promoted to signed int (since int can hold all values
of u8).  However, if hob_lbal is 128 or more, then it is treated as a
negative signed value and sign-extended when promoted to u64 to | into
sectors, which leads to the MSB 32 bits of section getting set
incorrectly.

For example, Phillip O'Donnell <phillip.odonnell@...il.com> reported
that a 1.5GB drive caused:

    ata3.00: HPA detected: current 2930277168, native 18446744072344861488

where 2930277168 == 0xAEA87B30 and 18446744072344861488 == 0xffffffffaea87b30
which shows the problem when hob_lbal is 0xae.

Fix this by adding a cast to u64, just as is used by for hob_lbah and
hob_lbam in the function.

Reported-by: Phillip O'Donnell <phillip.odonnell@...il.com>
Signed-off-by: Roland Dreier <rolandd@...co.com>
---
Phillip, this should fix at least your cosmetic issue; can you test it
and report back?

Thanks,
  Roland

 drivers/ata/libata-core.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index bbb3cae..10424ff 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -1268,7 +1268,7 @@ u64 ata_tf_to_lba48(const struct ata_taskfile *tf)
 
 	sectors |= ((u64)(tf->hob_lbah & 0xff)) << 40;
 	sectors |= ((u64)(tf->hob_lbam & 0xff)) << 32;
-	sectors |= (tf->hob_lbal & 0xff) << 24;
+	sectors |= ((u64)(tf->hob_lbal & 0xff)) << 24;
 	sectors |= (tf->lbah & 0xff) << 16;
 	sectors |= (tf->lbam & 0xff) << 8;
 	sectors |= (tf->lbal & 0xff);
--
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