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    SubjectRe: [PATCH] of: Prevent unaligned access in of_alias_scan()
    On Fri, Sep 23, 2016 at 4:38 PM, Paul Burton <paul.burton@imgtec.com> wrote:
    > When allocating a struct alias_prop, of_alias_scan() only requested that
    > it be aligned on a 4 byte boundary. The struct contains pointers which
    > leads to us attempting 64 bit writes on 64 bit systems, and if the CPU
    > doesn't support unaligned memory accesses then this causes problems -
    > for example on some MIPS64r2 CPUs including the "mips64r2-generic" QEMU
    > emulated CPU it will trigger an address error exception.
    >
    > Fix this by requesting alignment for the struct alias_prop allocation
    > matching that which the compiler expects, using the __alignof__ keyword.
    >
    > Signed-off-by: Paul Burton <paul.burton@imgtec.com>

    Looks right to me.

    Reviewed-by: Grant Likely <grant.likely@secretlab.ca>

    > Cc: devicetree@vger.kernel.org
    > Cc: Rob Herring <robh+dt@kernel.org>
    > Cc: Frank Rowand <frowand.list@gmail.com>
    > Cc: linux-kernel@vger.kernel.org
    > Cc: linux-mips@linux-mips.org
    > Cc: Ralf Baechle <ralf@linux-mips.org>
    > ---
    > drivers/of/base.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/drivers/of/base.c b/drivers/of/base.c
    > index 3ce6953..448aa40 100644
    > --- a/drivers/of/base.c
    > +++ b/drivers/of/base.c
    > @@ -2042,7 +2042,7 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
    > continue;
    >
    > /* Allocate an alias_prop with enough space for the stem */
    > - ap = dt_alloc(sizeof(*ap) + len + 1, 4);
    > + ap = dt_alloc(sizeof(*ap) + len + 1, __alignof__(*ap));
    > if (!ap)
    > continue;
    > memset(ap, 0, sizeof(*ap) + len + 1);
    > --
    > 2.10.0
    >

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