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From: Sascha Hauer <s.hauer@pengutronix.de>
To: Ahmad Fatoum <ahmad@a3f.at>
Cc: barebox@lists.infradead.org, afa@pengutronix.de
Subject: Re: [PATCH 5/5] commands: fix unaligned accesses of aliased commands on amd64
Date: Fri, 23 Aug 2019 09:36:56 +0200	[thread overview]
Message-ID: <20190823073656.6l2qzionxlbhxac4@pengutronix.de> (raw)
In-Reply-To: <20190822061941.6093-6-ahmad@a3f.at>

On Thu, Aug 22, 2019 at 08:19:41AM +0200, Ahmad Fatoum wrote:
> If a command has aliases (e.g. edit and sedit), register_command
> allocates a new struct command for the alias. As struct command has a
> alignment of 64 specified on __x86_64__, this new allocation needs to
> observe the alignment lest unaligned access could occur. I don't think
> it's likely that GCC would generate SIMD code here that expects a 64 byte
> alignment, but heed UBSan's advice and use xmemalign with the appropriate
> alignment.
> 
> Fixes: 8c14b97758 ("svn_rev_477")
> Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
> ---
> I am not sure about this, because I don't understand why there was a 64
> bit alignment in the x86_64 linker script in the first place.
> The fix is trivial though, so even if it's only a theoretical, lets have
> it?

Have you tried removing the alignment? AFAIK without it we are not able
to iterate over the commands array generated by the linker. I don't know
if this issue is still present. There is no requirement to align a
struct command to 64bit otherwise.

Sascha

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  reply	other threads:[~2019-08-23  7:36 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-22  6:19 [PATCH 0/5] sandbox: support -fsanitize={address,ubsan} Ahmad Fatoum
2019-08-22  6:19 ` [PATCH 1/5] sandbox: include header to provide missing prototype Ahmad Fatoum
2019-08-22  6:19 ` [PATCH 2/5] common: add generic CONFIG_UBSAN_SANITIZE_ALL plumbing Ahmad Fatoum
2019-08-22  6:19 ` [PATCH 3/5] common: add generic CONFIG_KASAN option Ahmad Fatoum
2019-08-22  6:19 ` [PATCH 4/5] sandbox: support Address and UndefinedBehavior sanitizers Ahmad Fatoum
2019-08-22  6:19 ` [PATCH 5/5] commands: fix unaligned accesses of aliased commands on amd64 Ahmad Fatoum
2019-08-23  7:36   ` Sascha Hauer [this message]
2019-08-23  9:08     ` Ahmad Fatoum
2019-08-23  9:13 ` [PATCH 0/5] sandbox: support -fsanitize={address,ubsan} Ahmad Fatoum
2019-08-23 12:31 ` Ahmad Fatoum

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