linux-kernel - Re: [PATCH v4 11/29] x86/dumpstack: When OOPSing, rewind the stack before do

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Message-ID: <20160704184500.GD7261@pd.tnic>
Date:	Mon, 4 Jul 2016 20:45:00 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Jann Horn <jann@...jh.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v4 11/29] x86/dumpstack: When OOPSing, rewind the stack
 before do_exit

On Sun, Jun 26, 2016 at 02:55:33PM -0700, Andy Lutomirski wrote:
> If we call do_exit with a clean stack, we greatly reduce the risk of

Nits:	    do_exit()

> recursive oopses due to stack overflow in do_exit, and we allow

s/ in do_exit//

> do_exit to work even if we OOPS from an IST stack.  The latter gives

Append "()" to the function names.

> us a much better chance of surviving long enough after we detect a
> stack overflow to write out our logs.
> 
> I intentionally separated this from the preceding patch that
> disables do_exit-on-OOPS on IST stacks.  This way, if we need to
> revert this patch, we still end up in an acceptable state wrt stack
> overflow handling.
> 
> Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---

...

> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index 352f022cfd5b..0d05f113805e 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -226,6 +226,8 @@ unsigned long oops_begin(void)
>  EXPORT_SYMBOL_GPL(oops_begin);
>  NOKPROBE_SYMBOL(oops_begin);
>  
> +extern void __noreturn rewind_stack_do_exit(int signr);

You don't need the "extern" here.

> +
>  void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
>  {
>  	if (regs && kexec_should_crash(current))
-- 
Regards/Gruss,
    Boris.

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