From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Jiri Kosina <jkosina@suse.cz>
Cc: x86@kernel.org, Borislav Petkov <bp@alien8.de>,
Kees Cook <keescook@chromium.org>,
Seth Jennings <sjenning@redhat.com>,
Vojtech Pavlik <vojtech@suse.cz>,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org
Subject: Re: [PATCH 2/2] livepatch: x86: make kASLR logic more accurate
Date: Tue, 28 Apr 2015 07:09:02 -0500 [thread overview]
Message-ID: <20150428120902.GB16487@treble.redhat.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1504271335020.16113@pobox.suse.cz>
On Mon, Apr 27, 2015 at 04:28:58PM +0200, Jiri Kosina wrote:
> We give up old_addr hint from the coming patch module in cases when kernel
> load base has been randomized (as in such case, the coming module has no
> idea about the exact randomization offset).
>
> We are currently too pessimistic, and give up immediately as soon as
> CONFIG_RANDOMIZE_BASE is set; this doesn't however directly imply that the
> load base has actually been randomized. There are config options that
> disable kASLR (such as hibernation), user could have disabled kaslr on
> kernel command-line, etc.
>
> The loader propagates the information whether kernel has been randomized
> through bootparams. This allows us to have the condition more accurate.
>
> On top of that, it seems unnecessary to give up old_addr hints even if
> randomization is active. The relocation offset can be computed using
> kaslr_ofsset(), and therefore old_addr can be adjusted accordingly.
>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
> arch/x86/include/asm/livepatch.h | 1 +
> kernel/livepatch/core.c | 5 +++--
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h
> index 2d29197..19c099a 100644
> --- a/arch/x86/include/asm/livepatch.h
> +++ b/arch/x86/include/asm/livepatch.h
> @@ -21,6 +21,7 @@
> #ifndef _ASM_X86_LIVEPATCH_H
> #define _ASM_X86_LIVEPATCH_H
>
> +#include <asm/setup.h>
> #include <linux/module.h>
> #include <linux/ftrace.h>
>
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 284e269..0e7c23c 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -234,8 +234,9 @@ static int klp_find_verify_func_addr(struct klp_object *obj,
> int ret;
>
> #if defined(CONFIG_RANDOMIZE_BASE)
> - /* KASLR is enabled, disregard old_addr from user */
> - func->old_addr = 0;
> + /* If KASLR has been enabled, adjust old_addr accordingly */
> + if (kaslr_enabled() && func->old_addr)
> + func->old_addr += kaslr_offset();
> #endif
>
> if (!func->old_addr || klp_is_module(obj))
> --
> Jiri Kosina
> SUSE Labs
--
Josh
next prev parent reply other threads:[~2015-04-28 12:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-27 14:27 [PATCH 0/2] introduce kaslr_offset() and its users Jiri Kosina
2015-04-27 14:28 ` [PATCH 1/2] x86: introduce kaslr_offset() Jiri Kosina
2015-04-28 12:08 ` Josh Poimboeuf
2015-04-28 15:15 ` [PATCH v2 " Jiri Kosina
2015-04-28 15:57 ` Jiri Kosina
2015-04-28 15:59 ` Borislav Petkov
2015-04-29 14:56 ` Jiri Kosina
2015-04-29 16:16 ` Jiri Kosina
2015-04-27 14:28 ` [PATCH 2/2] livepatch: x86: make kASLR logic more accurate Jiri Kosina
2015-04-27 14:41 ` Minfei Huang
2015-04-27 23:29 ` Jiri Kosina
2015-04-28 0:08 ` Minfei Huang
2015-04-28 12:09 ` Josh Poimboeuf [this message]
2015-04-29 14:56 ` Jiri Kosina
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