From: Andreas Dilger Subject: [PATCH] ext4: avoid setting directory i_nlink to zero Date: Tue, 25 Oct 2011 09:33:05 -0600 Message-ID: <1319556785-34754-1-git-send-email-adilger@whamcloud.com> Cc: linux-ext4@vger.kernel.org, Andreas Dilger To: tytso@mit.edu Return-path: Received: from idcmail-mo2no.shaw.ca ([64.59.134.9]:27880 "EHLO idcmail-mo2no.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752130Ab1JYPdt (ORCPT ); Tue, 25 Oct 2011 11:33:49 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: If a directory with more than EXT4_LINK_MAX subdirectories, the nlink count is set to 1. Subsequently, if any subdirectories are deleted, ext4_dec_count() decrements the i_nlink count, which may go to 0 temporarily before being incremented back to 1. While this is done under i_mutex, which prevents races for directory and inode operations that check i_nlink, the temporary i_nlink == 0 case is exposed to userspace via stat() and similar calls that do not hold i_mutex. Instead, change the code to not decrement i_nlink count for any directories that do not already have i_nlink larger than 2. Reported-by: Cliff White Reviewed-by: Johann Lombardi Signed-off-by: Andreas Dilger --- fs/ext4/namei.c | 5 ++--- 1 files changed, 2 insertions(+), 3 deletions(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 1c924fa..b13cd39 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -1707,9 +1707,8 @@ static void ext4_inc_count(handle_t *handle, struct inode *inode) */ static void ext4_dec_count(handle_t *handle, struct inode *inode) { - drop_nlink(inode); - if (S_ISDIR(inode->i_mode) && inode->i_nlink == 0) - inc_nlink(inode); + if (!S_ISDIR(inode->i_mode) || inode->i_nlink > 2) + drop_nlink(inode); } -- 1.7.3.4