linux-kernel - Re: [PATCH] vmacache: change vmacache_find() to always check ->vm

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Message-ID: <20140429140216.GA16816@redhat.com>
Date:	Tue, 29 Apr 2014 16:02:16 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	Davidlohr Bueso <davidlohr@...com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux MM <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] vmacache: change vmacache_find() to always check
	->vm_mm

On 04/29, Srivatsa S. Bhat wrote:
>
> On 04/29/2014 06:22 PM, Oleg Nesterov wrote:
> > On 04/29, Srivatsa S. Bhat wrote:
> >>
> >> I guess I'll hold off on testing this fix until I get to reproduce
> >> the bug more reliably..
> >
> > perhaps the patch below can help a bit?
> >
> > -------------------------------------------------------------------------------
> > Subject: [PATCH] vmacache: change vmacache_find() to always check ->vm_mm
> >
> > If ->vmacache was corrupted it would be better to detect and report
> > the problem asap, check vma->vm_mm before vm_start/vm_end.
> >
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> > ---
> >  mm/vmacache.c |    5 +++--
> >  1 files changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/vmacache.c b/mm/vmacache.c
> > index d4224b3..952a324 100644
> > --- a/mm/vmacache.c
> > +++ b/mm/vmacache.c
> > @@ -81,9 +81,10 @@ struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
> >  	for (i = 0; i < VMACACHE_SIZE; i++) {
> >  		struct vm_area_struct *vma = current->vmacache[i];
> >
> > -		if (vma && vma->vm_start <= addr && vma->vm_end > addr) {
> > +		if (vma) {
> >  			BUG_ON(vma->vm_mm != mm);
> > -			return vma;
> > +			if (vma->vm_start <= addr && vma->vm_end > addr)
> > +				return vma;
> >  		}
> >  	}
> >
>
> IIUC, this is similar to commit 50f5aa8a9b2 (mm: don't pointlessly use
> BUG_ON() for sanity check).

Yes, I see this commit after git-pull ;)

Please ignore then.

> But even with that commit included I was
> not able to reproduce the bug again, as reported here:
>
> https://lkml.org/lkml/2014/4/29/187

Thanks...

Oleg.

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