linux-kernel - Re: [RESEND 2][PATCH v4] hexdump: fix for non-aligned buffers

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Date:	Wed, 08 Jul 2015 16:49:02 -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: [RESEND 2][PATCH v4] hexdump: fix for non-aligned buffers

On Thu, 2015-07-09 at 01:44 +0200, Horacio Mijail Antón Quiles wrote:
> An hexdump with a buf not aligned to the groupsize causes
> non-naturally-aligned memory accesses. This was causing a kernel panic on
> the processor BlackFin BF527, when such an unaligned buffer was fed by the
> function ubifs_scanned_corruption in fs/ubifs/scan.c .

Seems sensible enough to me.

> ---
> diff --git a/lib/hexdump.c b/lib/hexdump.c
[]
> @@ -124,6 +124,11 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
>  	if ((len % groupsize) != 0)	/* no mixed size output */
>  		groupsize = 1;
>  
> +	/* fall back to 1-byte groups if buf is not aligned to groupsize */
> +	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
> +	    !IS_ALIGNED((uintptr_t)buf, groupsize))
> +		groupsize = 1;
> +
>  	ngroups = len / groupsize;
>  	ascii_column = rowsize * 2 + rowsize / groupsize + 1;
>  


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