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    SubjectRe: [PATCH] libata: Avoid overflow in ata_tf_to_lba48() when tf->hba_lbal > 127
    Confirmed - HPA is no longer detected on boot.

    Cheers,
    Phillip

    On Wed, Oct 29, 2008 at 12:52 PM, Roland Dreier <rdreier@cisco.com> 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>
    > ---
    > 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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