Message-ID: <4909023E.60806@shaw.ca>
Date: Wed, 29 Oct 2008 18:39:26 -0600
From: Robert Hancock <hancockr@shaw.ca>
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To: Roland Dreier <rdreier@cisco.com>
CC: "Phillip O'Donnell" <phillip.odonnell@gmail.com>, jeff@garzik.org,
       Oskar Liljeblad <oskar@osk.mine.nu>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] libata: Avoid overflow in ata_tf_to_lba48() when tf->hba_lbal
 > 127
References: <fa.01zEaARwrup2dCOTuHTYxzuS9BI@ifi.uio.no> <fa.Dwk+NgWNu7+JRcsgOPCxSr7y5SQ@ifi.uio.no> <fa.fIxdVik0iPc+lS+sd5ef+ZoALzQ@ifi.uio.no>
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Roland Dreier wrote:
> 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@gmail.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@gmail.com>
> Signed-off-by: Roland Dreier <rolandd@cisco.com>

This should be pushed to -stable as well once it's merged..
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