linux-kernel - Re: [PATCH] more sanity checks in Dwarf2 unwinder

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Date:	Wed, 29 Nov 2006 14:14:55 +0100
From:	Andi Kleen <ak@...e.de>
To:	"Jan Beulich" <jbeulich@...ell.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] more sanity checks in Dwarf2 unwinder

On Wednesday 29 November 2006 12:13, Jan Beulich wrote:
> Tighten the requirements on both input to and output from the Dwarf2
> unwinder.

Thanks for doing this.

>  	while (unwind(info) == 0 && UNW_PC(info)) {
>  		n++;
>  		oad->ops->address(oad->data, UNW_PC(info));
>  		if (arch_unw_user_mode(info))
>  			break;
> +		if ((sp & ~(PAGE_SIZE - 1)) == (UNW_SP(info) & ~(PAGE_SIZE - 1))
> +		    && sp > UNW_SP(info))
> +			break;

Hmm, but that wouldn't catch the case when the SP is completely
corrupted for some reason.
Maybe it would be better to just run a brute force check here like 
the old in_exception_stack(). Similar on x86-64.

> +	if (UNW_PC(frame) % state.codeAlign
> +	    || UNW_SP(frame) % sleb128abs(state.dataAlign)
> +	    || (pc == UNW_PC(frame) && sp == UNW_SP(frame)))
> +		return -EIO;

Would it be possible to add printks for the EIOs? We want to know 
when dwarf2 is corrupted.

-Andi
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