linux-kernel - Re: [PATCH] hexdump: fix for non-naturally-aligned buffers

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Date:	Sun, 21 Jun 2015 09:47:05 -0700
From:	Joe Perches <joe@...ches.com>
To:	Horacio Mijail Antón Quiles <hmijail@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	David Howells <dhowells@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>, linux-kernel@...r.kernel.org,
	trivial@...nel.org
Subject: Re: [PATCH] hexdump: fix for non-naturally-aligned buffers

On Sun, 2015-06-21 at 18:36 +0200,
=?UTF-8?q?Horacio=20Mijail=20Ant=C3=B3n=20Quiles?= wrote:
> Calling hex_dump_to_buffer() with a buffer non-naturally-aligned to the
> groupsize causes non-naturally-aligned memory accesses. This was causing
> a kernel panic on the BlackFin BF527, when such a call was made by 
> ubifs_scanned_corruption() in fs/ubifs/scan.c .
[]
> diff --git a/lib/hexdump.c b/lib/hexdump.c
[]
> @@ -123,6 +123,11 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
>  		groupsize = 1;
>  	if ((len % groupsize) != 0)	/* no mixed size output */
>  		groupsize = 1;
> +	
> +	/* fall back to 1-byte groups if buf is not naturally aligned */
> +	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
> +	    (((uintptr_t)buf % groupsize) != 0))
> +		groupsize = 1;

Maybe !IS_ALIGNED(buf, groupsize) reads better.


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