linux-kernel - Re: [PATCH] xen/setup: add paranoid index check and warning

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Message-ID: <543D2D66.7040000@martingkelly.com>
Date:	Tue, 14 Oct 2014 07:04:22 -0700
From:	Martin Kelly <martin@...tingkelly.com>
To:	David Vrabel <david.vrabel@...rix.com>,
	xen-devel@...ts.xenproject.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
CC:	konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
	tglx@...utronix.de, mingo@...hat.com,
	Martin Kelly <martkell@...zon.com>
Subject: Re: [PATCH] xen/setup: add paranoid index check and warning

On 10/14/2014 02:22 AM, David Vrabel wrote:
> On 14/10/14 02:19, Martin Kelly wrote:
>> In a call to set_phys_range_identity, i-1 is used without checking that
>> i is non-zero. Although unlikely, a bug in the code before it could
>> cause the value to be 0, leading to erroneous behavior. This patch adds
>> a check against 0 value and a corresponding warning.
> 
> This can only happen if the toolstack supplies a memory map with zero
> entries.  I could see justification for adding a panic at the top of
> this function in this case, but I can't see the usefulness of this warning.
> 

Yes, a panic is probably appropriate. What do you think about the relative merits of panicing in the callers vs. in the sanitize_e820_map function itself (thus to avoid a bunch of similar error checks in the callers)?
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