From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762188AbXHVJBI (ORCPT ); Wed, 22 Aug 2007 05:01:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758578AbXHVIxX (ORCPT ); Wed, 22 Aug 2007 04:53:23 -0400 Received: from 1wt.eu ([62.212.114.60]:2049 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758389AbXHVIxW (ORCPT ); Wed, 22 Aug 2007 04:53:22 -0400 From: Willy Tarreau Message-Id: <20070822084021.%N@1wt.eu> References: <20070822083844.%N@1wt.eu> User-Agent: quilt/0.46-1 Date: Wed, 22 Aug 2007 11:39:14 +0200 To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Greg Banks , "J. Bruce Fields" , NeilBrown , Andrew Morton , Greg Kroah-Hartman , Willy Tarreau Subject: [2.6.20.17 review 30/58] nfsd: fix possible read-ahead cache and export table corruption Content-Disposition: inline; filename=0030-nfsd-fix-possible-read-ahead-cache-and-export-table.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org The value of nperbucket calculated here is too small--we should be rounding up instead of down--with the result that the index j in the following loop can overflow the raparm_hash array. At least in my case, the next thing in memory turns out to be export_table, so the symptoms I see are crashes caused by the appearance of four zeroed-out export entries in the first bucket of the hash table of exports (which were actually entries in the readahead cache, a pointer to which had been written to the export table in this initialization code). It looks like the bug was probably introduced with commit fce1456a19f5c08b688c29f00ef90fdfa074c79b ("knfsd: make the readahead params cache SMP-friendly"). Cc: Greg Banks Signed-off-by: "J. Bruce Fields" Acked-by: NeilBrown Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- fs/nfsd/vfs.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 8283236..d8b773a 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1887,7 +1887,7 @@ nfsd_racache_init(int cache_size) raparm_hash[i].pb_head = NULL; spin_lock_init(&raparm_hash[i].pb_lock); } - nperbucket = cache_size >> RAPARM_HASH_BITS; + nperbucket = DIV_ROUND_UP(cache_size, RAPARM_HASH_SIZE); for (i = 0; i < cache_size - 1; i++) { if (i % nperbucket == 0) raparm_hash[j++].pb_head = raparml + i; -- 1.5.2.5 --