linux-kernel - Re: [PATCH] crash_core: optimize crash_exclude_mem

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Date: Sat, 30 Dec 2023 18:28:06 +0800
From: Baoquan He <bhe@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Yuntao Wang <ytcoode@...il.com>, bp@...en8.de,
	dave.hansen@...ux.intel.com, dyoung@...hat.com,
	hbathini@...ux.ibm.com, hpa@...or.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, mingo@...hat.com, seanjc@...gle.com,
	tglx@...utronix.de, tiwai@...e.de, vgoyal@...hat.com,
	x86@...nel.org
Subject: Re: [PATCH] crash_core: optimize crash_exclude_mem_range()

On 12/29/23 at 12:10pm, Andrew Morton wrote:
> On Wed, 20 Dec 2023 00:34:18 +0800 Yuntao Wang <ytcoode@...il.com> wrote:
> 
> > Because memory ranges in mem->ranges are stored in ascending order, when we
> > detect `p_end < start`, we can break the for loop early, as the subsequent
> > memory ranges must also be outside the range we are looking for.
> > 
> > Signed-off-by: Yuntao Wang <ytcoode@...il.com>
> > ---
> > Hi Andrew,
> > 
> > Patch "[PATCH 2/2] crash_core: fix out-of-bounds access check in
> > crash_exclude_mem_range()" can be ignored, use this patch instead.
> > 
> 
> Some reviewer input on this would be helpful please?


I suggested this in below discussion thread:
https://lore.kernel.org/all/ZYEOshALGbDKwSdc@MiWiFi-R3L-srv/T/#u

So it would be good if squashing this into patch 3 of another patch
thread you are asking:
[PATCH 3/3] crash_core: fix and simplify the logic of crash_exclude_mem_range()

And I would suggest withdrawing Yuntao's below patch on your
mm-nonmm-unstable branch.

961c69e9f1bf x86/crash: fix potential cmem->ranges array overflow

Becase there's better one to fix the potential oob from fuqiang,
although fuqiang need improve his patch log.

[PATCH v3] x86/kexec: fix potential cmem->ranges out of bounds
https://lore.kernel.org/all/20231222121855.148215-1-fuqiang.wang@easystack.cn/T/#u

> 
> > --- a/kernel/crash_core.c
> > +++ b/kernel/crash_core.c
> > @@ -575,9 +575,12 @@ int crash_exclude_mem_range(struct crash_mem *mem,
> >  		p_start = mstart;
> >  		p_end = mend;
> >  
> > -		if (p_start > end || p_end < start)
> > +		if (p_start > end)
> >  			continue;
> >  
> > +		if (p_end < start)
> > +			break;
> > +
> >  		/* Truncate any area outside of range */
> >  		if (p_start < start)
> >  			p_start = start;
> > -- 
> > 2.43.0
>