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Date: Tue, 28 Apr 2015 07:28:02 -0700
From: Dave Hansen <dave.hansen@intel.com>
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To: Fenghua Yu <fenghua.yu@intel.com>, "H. Peter Anvin" <hpa@linux.intel.com>,
        Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        Asit K Mallick <asit.k.mallick@intel.com>,
        Glenn Williamson <glenn.p.williamson@intel.com>
CC: linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
        Fengguang Wu <fengguang.wu@intel.com>
Subject: Re: [PATCH Bugfix v2 2/4] x86/xsaves: Define and use user_xstate_size
 for xstate size in signal context
References: <1429678319-61356-1-git-send-email-fenghua.yu@intel.com> <1429678319-61356-3-git-send-email-fenghua.yu@intel.com>
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On 04/21/2015 09:51 PM, Fenghua Yu wrote:
> +static int copy_to_user_xstate(void __user *buf_fx, struct xsave_struct *xsave)
> +{
...
> +			if (__copy_to_user(buf_fx + user_offset,
> +				     xsave + kernel_offset, size))
> +				return -1;
> +		}
> +	}
> +

0day found this, but I'm replying to the original thread.

> [   13.595511] BUG: KASan: out of bounds access in save_xstate_sig+0x1bf/0x470 at addr ffff880000184208
> [   13.596280] Read of size 8 by task init/1

copy_to_user_xstate() gets inlined in to save_xstate_sig().  The read
probably means that this was an access to 'xsave' since we are reading a
kernel structure out to userspace.

'xsave' is a 'struct xsave_struct *' and yet it's being incremented like
'buf_fx' which is a 'void *'.