linux-kernel - [PATCH] [110/275] NFSD: memory corruption due to writing beyond the stat array

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Message-Id: <20110330210549.78C6E3E1A05@tassilo.jf.intel.com>
Date:	Wed, 30 Mar 2011 14:05:49 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	khorenko@...allels.com, khorenko@...nvz.org, bfields@...hat.com,
	gregkh@...e.de, ak@...ux.intel.com, linux-kernel@...r.kernel.org,
	stable@...nel.org, tim.bird@...sony.com
Subject: [PATCH] [110/275] NFSD: memory corruption due to writing beyond the stat array

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Konstantin Khorenko <khorenko@...allels.com>

commit 3aa6e0aa8ab3e64bbfba092c64d42fd1d006b124 upstream.

If nfsd fails to find an exported via NFS file in the readahead cache, it
should increment corresponding nfsdstats counter (ra_depth[10]), but due to a
bug it may instead write to ra_depth[11], corrupting the following field.

In a kernel with NFSDv4 compiled in the corruption takes the form of an
increment of a counter of the number of NFSv4 operation 0's received; since
there is no operation 0, this is harmless.

In a kernel with NFSDv4 disabled it corrupts whatever happens to be in the
memory beyond nfsdstats.

Signed-off-by: Konstantin Khorenko <khorenko@...nvz.org>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 fs/nfsd/vfs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.35.y/fs/nfsd/vfs.c
===================================================================
--- linux-2.6.35.y.orig/fs/nfsd/vfs.c	2011-03-29 22:51:24.834087726 -0700
+++ linux-2.6.35.y/fs/nfsd/vfs.c	2011-03-29 23:03:00.482287829 -0700
@@ -819,7 +819,7 @@
 		if (ra->p_count == 0)
 			frap = rap;
 	}
-	depth = nfsdstats.ra_size*11/10;
+	depth = nfsdstats.ra_size;
 	if (!frap) {	
 		spin_unlock(&rab->pb_lock);
 		return NULL;
--
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