linux-kernel - Re: [PATCH] x86: Increase exception stack sizes

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Message-ID: <0278349e-3a6d-9ebd-6cc3-490fb99d1990@linux.alibaba.com>
Date:   Thu, 16 Sep 2021 11:42:22 +0800
From:   王贇 <yun.wang@...ux.alibaba.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "open list:X86 MM" <linux-kernel@...r.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <netdev@...r.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <bpf@...r.kernel.org>
Subject: Re: [PATCH] x86: Increase exception stack sizes



On 2021/9/15 下午11:19, Peter Zijlstra wrote:
> On Wed, Sep 15, 2021 at 03:34:20PM +0800, 王贇 wrote:
>> Hi, Dave, Peter
>>
>> What if we just increase the stack size when ftrace enabled?
> 
> I think we can do an unconditional increase. But please first test that
> guard page patch :-)

Nice~ let's focus on the guard one firstly.

Regards,
Michael Wang

> 
> ---
> Subject: x86: Increase exception stack sizes
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Wed Sep 15 16:19:46 CEST 2021
> 
> It turns out that a single page of stack is trivial to overflow with
> all the tracing gunk enabled. Raise the exception stacks to 2 pages,
> which is still half the interrupt stacks, which are at 4 pages.
> 
> Reported-by: Michael Wang <yun.wang@...ux.alibaba.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/include/asm/page_64_types.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/arch/x86/include/asm/page_64_types.h
> +++ b/arch/x86/include/asm/page_64_types.h
> @@ -15,7 +15,7 @@
>  #define THREAD_SIZE_ORDER	(2 + KASAN_STACK_ORDER)
>  #define THREAD_SIZE  (PAGE_SIZE << THREAD_SIZE_ORDER)
>  
> -#define EXCEPTION_STACK_ORDER (0 + KASAN_STACK_ORDER)
> +#define EXCEPTION_STACK_ORDER (1 + KASAN_STACK_ORDER)
>  #define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
>  
>  #define IRQ_STACK_ORDER (2 + KASAN_STACK_ORDER)
>