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SubjectRe: [PATCH] Fix an inproper alignment accessing in irda protocol stack
On Thu, 8 Jun 2006 15:15:11 +0800
"Luke Yang" <luke.adi@gmail.com> wrote:

> Hi all,
>
> For "struct irda_device_info" in irda.h:
> struct irda_device_info {
> __u32 saddr; /* Address of local interface */
> __u32 daddr; /* Address of remote device */
> char info[22]; /* Description */
> __u8 charset; /* Charset used for description */
> __u8 hints[2]; /* Hint bits */
> };
> The "hints" member aligns at the third byte of a word, an odd
> address. So if we visit "hints" as a short in irlmp.c:
>
> u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
>
> will cause alignment problem on some machines. Architectures with
> strict alignment rules do not allow 16-bit read on an odd address.
>
> Signed-off-by: Luke Yang <luke.adi@gmail.com>
>
> irlmp.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletion(-)
>
> --- net/irda/irlmp.c.old 2006-06-08 14:49:20.000000000 +0800
> +++ net/irda/irlmp.c 2006-06-08 14:54:29.000000000 +0800
> @@ -849,7 +849,8 @@
> }
>
> /* Construct new discovery info to be used by IrLAP, */
> - u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
> + irlmp->discovery_cmd.data.hints[0] = irlmp->hints.word & 0xff;
> + irlmp->discovery_cmd.data.hints[1] = (irlmp->hints.word & 0xff00) >> 8;

This change will have the effect of swapping those two bytes on big-endian
machines.

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