linux-kernel - Re: [PATCH] livepatch: x86: bugfix about kASLR

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Date:	Wed, 04 Nov 2015 13:27:33 +0100
From:	"Cyril B." <cbay@...aysdata.com>
To:	Zhou Chengming <zhouchengming1@...wei.com>
CC:	jpoimboe@...hat.com, sjenning@...hat.com, jkosina@...e.cz,
	vojtech@...e.cz, live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org, guohanjun@...wei.com,
	huawei.libin@...wei.com, xiexiuqi@...wei.com
Subject: Re: [PATCH] livepatch: x86: bugfix about kASLR

Zhou Chengming wrote:
> When enable KASLR, func->old_addr will be set to zero
> and livepatch will find the right old address.
> But for reloc, livepatch just verify it using reloc->val
> (old addr from user), so verify failed and report
> "kernel mismatch" error.
>
> Reported-by: Cyril B.<cbay@...aysdata.com>
> Signed-off-by: Zhou Chengming<zhouchengming1@...wei.com>
> ---
>   kernel/livepatch/core.c |    7 ++++++-
>   1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 53196e2..c8885c6 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -311,7 +311,12 @@ static int klp_write_object_relocations(struct module *pmod,
>   		return -EINVAL;
>
>   	for (reloc = obj->relocs; reloc->name; reloc++) {
> -		if (!klp_is_module(obj)) {
> +
> +#if defined(CONFIG_RANDOMIZE_BASE)
> +		/* KASLR is enabled, disregard old_addr from user */
> +		reloc->val = 0;
> +#endif
> +		if (reloc->val&&  !klp_is_module(obj)) {
>   			ret = klp_verify_vmlinux_symbol(reloc->name,
>   							reloc->val);
>   			if (ret)

I still get the 'symbol not found in symbol table' error with that patch 
(on top of Linux 4.3).

Cyril
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