From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. Bruce Fields" Subject: [PATCH 1/5] nfsd: fix possible read-ahead cache and export table corruption Date: Wed, 18 Jul 2007 18:57:26 -0400 Message-ID: <11847994502502-git-send-email-bfields@fieldses.org> References: <20070713114228.3c171a90.akpm@linux-foundation.org> <11847994502579-git-send-email-bfields@fieldses.org> Cc: NeilBrown , nfs@lists.sourceforge.net, linux-kernel@vger.kernel.org, andros@citi.umich.edu, "J. Bruce Fields" , stable@kernel.org, Greg Banks To: Andrew Morton Return-path: In-Reply-To: <11847994502579-git-send-email-bfields@fieldses.org> Message-Id: <2ac9f179334dc7894bb58b1c2fb62837a07fbbdf.1184798679.git.bfields@citi.umich.edu> Sender: linux-kernel-owner@vger.kernel.org List-ID: From: J. Bruce Fields 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: stable@kernel.org Cc: Greg Banks Signed-off-by: "J. Bruce Fields" --- 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 e90f4a8..b8da5dd 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1916,7 +1916,7 @@ 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; -- 1.5.3.rc2