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From: "H. Peter Anvin" <hpa@zytor.com>
To: Baoquan He <bhe@redhat.com>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
	mingo@redhat.com, x86@kernel.org, vgoyal@redhat.com,
	keescook@chromium.org, ak@linux.intel.com, ebiederm@xmission.com,
	kexec@lists.infradead.org, whissi@whissi.de,
	kumagai-atsushi@mxc.nes.nec.co.jp, stable@vger.kernel.org
Subject: Re: [resend Patch v3 1/2] kaslr: check if kernel location is changed
Date: Tue, 30 Sep 2014 14:21:05 -0700	[thread overview]
Message-ID: <542B1EC1.8090502@zytor.com> (raw)
In-Reply-To: <1412060896-1902-1-git-send-email-bhe@redhat.com>

On 09/30/2014 12:08 AM, Baoquan He wrote:
> Function handle_relocations() is used to do the relocations handling
> for i686 and kaslr of x86_64. For 32 bit the relocation handling is
> mandotary to perform. For x86_64 only when kaslr is enabled and a
> random kernel location is chosen successfully the relocation handling
> shound be done. However previous implementation only compared the
> kernel loading address and LOAD_PHYSICAL_ADDR where kernel were
> compiled to run at. This would casue system to be exceptional in
> few conditions like when delta between load address and compiled
> address is bigger than what 32bit signed relocations can handle.
> Also there will be limitations that delta can't be too big otherwise
> kernel text virtual addresses will overflow in module address space.
> 
> So in this patch check if kernel location is changed after
> choose_kernel_location() when x86_64. If and only if in x86_64
> and kernel location is changed, we say a kaslr random kernel
> location is chosen, then the relocation handling is needed.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> Acked-by: Vivek Goyal <vgoyal@redhat.com>
> Acked-by: Kees Cook <keescook@chromium.org>
> Tested-by: Thomas D. <whissi@whissi.de>
> Cc: stable@vger.kernel.org

Could you clarify under what conditions we may end up with 32-bit signed
overflow, and yet have a functional kernel?

	-hpa



  parent reply	other threads:[~2014-09-30 21:22 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-30  7:08 [resend Patch v3 1/2] kaslr: check if kernel location is changed Baoquan He
2014-09-30  7:08 ` [resend Patch v3 2/2] export the kernel image size KERNEL_IMAGE_SIZE Baoquan He
2015-02-02  7:32   ` Baoquan He
2015-02-09 20:18     ` Kees Cook
2014-09-30 21:21 ` H. Peter Anvin [this message]
2014-10-01 13:52   ` [resend Patch v3 1/2] kaslr: check if kernel location is changed Vivek Goyal
2014-10-08 15:09     ` H. Peter Anvin
2014-10-08 19:27       ` Vivek Goyal
2014-10-11  3:14         ` Baoquan He
2014-10-11 10:34           ` H. Peter Anvin
2014-10-11 12:38             ` Baoquan He
2014-10-11 12:44               ` Baoquan He
2014-10-13 12:52             ` Vivek Goyal
2014-10-13 15:19               ` Vivek Goyal
2014-10-13 15:43                 ` H. Peter Anvin
2014-10-13 17:22                   ` Vivek Goyal
2014-10-14 12:49                     ` Vivek Goyal
2014-10-15  3:37                       ` Baoquan He
2014-10-15 20:22                         ` Vivek Goyal
2014-10-15 20:32                         ` H. Peter Anvin
2014-10-15 23:55                           ` Baoquan He
2014-10-15 23:58                             ` Baoquan He
2014-10-28  5:04                         ` Baoquan He
2014-10-08 14:40   ` Baoquan He
2015-01-09  2:09 ` Baoquan He

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