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

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Date:	Tue, 29 Apr 2014 14:52:55 +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: [PATCH] vmacache: change vmacache_find() to always check ->vm_mm

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;
 		}
 	}
 
-- 
1.5.5.1


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