Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-qc0-f182.google.com ([209.85.216.182]:52089 "EHLO mail-qc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753083AbaIDMjR (ORCPT ); Thu, 4 Sep 2014 08:39:17 -0400 Received: by mail-qc0-f182.google.com with SMTP id m20so10481485qcx.27 for ; Thu, 04 Sep 2014 05:39:17 -0700 (PDT) From: Jeff Layton To: linux-fsdevel@vger.kernel.org Cc: linux-nfs@vger.kernel.org, Christoph Hellwig , "J. Bruce Fields" , linux-kernel@vger.kernel.org Subject: [PATCH v2 03/17] locks: close potential race in lease_get_mtime Date: Thu, 4 Sep 2014 08:38:29 -0400 Message-Id: <1409834323-7171-4-git-send-email-jlayton@primarydata.com> In-Reply-To: <1409834323-7171-1-git-send-email-jlayton@primarydata.com> References: <1409834323-7171-1-git-send-email-jlayton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: lease_get_mtime is called without the i_lock held, so there's no guarantee about the stability of the list. Between the time when we assign "flock" and then dereference it to check whether it's a lease and for write, the lease could be freed. Ensure that that doesn't occur by taking the i_lock before trying to check the lease. Cc: J. Bruce Fields Signed-off-by: Jeff Layton Reviewed-by: Christoph Hellwig --- fs/locks.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 18e87f11a25f..4031324e6cca 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -1456,8 +1456,18 @@ EXPORT_SYMBOL(__break_lease); */ void lease_get_mtime(struct inode *inode, struct timespec *time) { - struct file_lock *flock = inode->i_flock; - if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK)) + bool has_lease = false; + struct file_lock *flock; + + if (inode->i_flock) { + spin_lock(&inode->i_lock); + flock = inode->i_flock; + if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK)) + has_lease = true; + spin_unlock(&inode->i_lock); + } + + if (has_lease) *time = current_fs_time(inode->i_sb); else *time = inode->i_mtime; -- 1.9.3