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Subject: Re: [PATCH v2 1/2] x86: corruption-check: Passing
 memory_corruption_check to command line causes panic
To:     <tglx@linutronix.de>, <mingo@redhat.com>, <hpa@zytor.com>,
        <x86@kernel.org>, <pombredanne@nexb.com>,
        <gregkh@linuxfoundation.org>, <kstewart@linuxfoundation.org>,
        <linux-kernel@vger.kernel.org>
References: <1534260823-87917-1-git-send-email-zhe.he@windriver.com>
From:   He Zhe <zhe.he@windriver.com>
Message-ID: <129aaffb-7f8d-cf84-cf2d-8e95e303908a@windriver.com>
Date:   Mon, 20 Aug 2018 16:56:22 +0800
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Could you please provide your input? Thanks.

Zhe

On 2018年08月14日 23:33, zhe.he@windriver.com wrote:
> From: He Zhe <zhe.he@windriver.com>
>
> memory_corruption_check[{_period|_size}]'s handlers do not check input
> argument before passing it to kstrtoul or simple_strtoull. The argument
> would be a NULL pointer if each of the kernel parameters, without its
> value, is set in command line and thus cause the following panic.
>
> PANIC: early exception 0xe3 IP 10:ffffffff73587c22 error 0 cr2 0x0
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.18-rc8+ #2
> [    0.000000] RIP: 0010:kstrtoull+0x2/0x10
> ...
> [    0.000000] Call Trace
> [    0.000000]  ? set_corruption_check+0x21/0x49
> [    0.000000]  ? do_early_param+0x4d/0x82
> [    0.000000]  ? parse_args+0x212/0x330
> [    0.000000]  ? rdinit_setup+0x26/0x26
> [    0.000000]  ? parse_early_options+0x20/0x23
> [    0.000000]  ? rdinit_setup+0x26/0x26
> [    0.000000]  ? parse_early_param+0x2d/0x39
> [    0.000000]  ? setup_arch+0x2f7/0xbf4
> [    0.000000]  ? start_kernel+0x5e/0x4c2
> [    0.000000]  ? load_ucode_bsp+0x113/0x12f
> [    0.000000]  ? secondary_startup_64+0xa5/0xb0
>
> This patch adds checks to prevent the panic.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
> v2:
> - Split out printk cleanups
> - Add cc to stable@vger.kernel.org
> - Use more meaningful error message
>
>  arch/x86/kernel/check.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/arch/x86/kernel/check.c b/arch/x86/kernel/check.c
> index 3339942..cc8258a 100644
> --- a/arch/x86/kernel/check.c
> +++ b/arch/x86/kernel/check.c
> @@ -31,6 +31,11 @@ static __init int set_corruption_check(char *arg)
>  	ssize_t ret;
>  	unsigned long val;
>  
> +	if (!arg) {
> +		pr_err("memory_corruption_check config string not provided\n");
> +		return -EINVAL;
> +	}
> +
>  	ret = kstrtoul(arg, 10, &val);
>  	if (ret)
>  		return ret;
> @@ -45,6 +50,11 @@ static __init int set_corruption_check_period(char *arg)
>  	ssize_t ret;
>  	unsigned long val;
>  
> +	if (!arg) {
> +		pr_err("memory_corruption_check_period config string not provided\n");
> +		return -EINVAL;
> +	}
> +
>  	ret = kstrtoul(arg, 10, &val);
>  	if (ret)
>  		return ret;
> @@ -59,6 +69,11 @@ static __init int set_corruption_check_size(char *arg)
>  	char *end;
>  	unsigned size;
>  
> +	if (!arg) {
> +		pr_err("memory_corruption_check_size config string not provided\n");
> +		return -EINVAL;
> +	}
> +
>  	size = memparse(arg, &end);
>  
>  	if (*end == '\0')