Re: [PATCH] Fix an inproper alignment accessing in irda protocol stack

[David Miller <davem@davemloft.net>]

From: "Luke Yang" <luke.adi@gmail.com>
Date: Wed, 14 Jun 2006 10:29:19 +0800

> --- net/irda/irlmp.c.old        2006-06-08 14:49:20.000000000 +0800
> +++ net/irda/irlmp.c    2006-06-14 10:00:22.000000000 +0800
> @@ -849,7 +849,10 @@
>         }
> 
>         /* Construct new discovery info to be used by IrLAP, */
> -       u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
> +       irlmp->discovery_cmd.data.hints[0] = \
> +               le16_to_cpu(irlmp->hints.word) & 0xff;
> +       irlmp->discovery_cmd.data.hints[1] = \
> +               (le16_to_cpu(irlmp->hints.word) & 0xff00) >> 8;
> 
>         /*
>          *  Set character set for device name (we use ASCII), and

I decided in the end to fix this differently.

We have a portable unaligned access interface, via get_unaligned() and
put_unaligned() in asm/unaligned.h, which makes sure there is no
penalty for platforms whose cpu does unaligned memory accesses
transparently.

diff --git a/net/irda/irlmp.c b/net/irda/irlmp.c
index c19e9ce..57ea160 100644
--- a/net/irda/irlmp.c
+++ b/net/irda/irlmp.c
@@ -44,6 +44,8 @@
 #include <net/irda/irlmp.h>
 #include <net/irda/irlmp_frame.h>
 
+#include <asm/unaligned.h>
+
 static __u8 irlmp_find_free_slsap(void);
 static int irlmp_slsap_inuse(__u8 slsap_sel);
 
@@ -840,6 +842,7 @@ void irlmp_do_expiry(void)
 void irlmp_do_discovery(int nslots)
 {
 	struct lap_cb *lap;
+	__u16 *data_hintsp;
 
 	/* Make sure the value is sane */
 	if ((nslots != 1) && (nslots != 6) && (nslots != 8) && (nslots != 16)){
@@ -849,7 +852,8 @@ void irlmp_do_discovery(int nslots)
 	}
 
 	/* Construct new discovery info to be used by IrLAP, */
-	u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
+	data_hintsp = (__u16 *) irlmp->discovery_cmd.data.hints;
+	put_unaligned(irlmp->hints.word, data_hintsp);
 
 	/*
 	 *  Set character set for device name (we use ASCII), and