Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759312AbcCDJHy (ORCPT ); Fri, 4 Mar 2016 04:07:54 -0500 Received: from mx2.suse.de ([195.135.220.15]:59849 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759141AbcCDJD4 (ORCPT ); Fri, 4 Mar 2016 04:03:56 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Jeff Layton , Alexander Viro , Jiri Slaby Subject: [PATCH 3.12 114/116] locks: fix unlock when fcntl_setlk races with a close Date: Fri, 4 Mar 2016 10:02:39 +0100 Message-Id: <2da2c15ffb7ed572f0d504cb1bd97fd66f3d9186.1457082108.git.jslaby@suse.cz> X-Mailer: git-send-email 2.7.2 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4015 Lines: 123 From: Jeff Layton 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 7f3697e24dc3820b10f445a4a7d914fc356012d1 upstream. Dmitry reported that he was able to reproduce the WARN_ON_ONCE that fires in locks_free_lock_context when the flc_posix list isn't empty. The problem turns out to be that we're basically rebuilding the file_lock from scratch in fcntl_setlk when we discover that the setlk has raced with a close. If the l_whence field is SEEK_CUR or SEEK_END, then we may end up with fl_start and fl_end values that differ from when the lock was initially set, if the file position or length of the file has changed in the interim. Fix this by just reusing the same lock request structure, and simply override fl_type value with F_UNLCK as appropriate. That ensures that we really are unlocking the lock that was initially set. While we're there, make sure that we do pop a WARN_ON_ONCE if the removal ever fails. Also return -EBADF in this event, since that's what we would have returned if the close had happened earlier. Cc: Alexander Viro Fixes: c293621bbf67 (stale POSIX lock handling) Reported-by: Dmitry Vyukov Signed-off-by: Jeff Layton Acked-by: "J. Bruce Fields" Signed-off-by: Jiri Slaby --- fs/locks.c | 51 ++++++++++++++++++++++++++++++--------------------- 1 file changed, 30 insertions(+), 21 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 0d2b5febc627..c8779651ccc7 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -1971,7 +1971,6 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, goto out; } -again: error = flock_to_posix_lock(filp, file_lock, &flock); if (error) goto out; @@ -2002,19 +2001,22 @@ again: * Attempt to detect a close/fcntl race and recover by * releasing the lock that was just acquired. */ - /* - * we need that spin_lock here - it prevents reordering between - * update of inode->i_flock and check for it done in close(). - * rcu_read_lock() wouldn't do. - */ - spin_lock(¤t->files->file_lock); - f = fcheck(fd); - spin_unlock(¤t->files->file_lock); - if (!error && f != filp && flock.l_type != F_UNLCK) { - flock.l_type = F_UNLCK; - goto again; + if (!error && file_lock->fl_type != F_UNLCK) { + /* + * We need that spin_lock here - it prevents reordering between + * update of inode->i_flock and check for it done in + * close(). rcu_read_lock() wouldn't do. + */ + spin_lock(¤t->files->file_lock); + f = fcheck(fd); + spin_unlock(¤t->files->file_lock); + if (f != filp) { + file_lock->fl_type = F_UNLCK; + error = do_lock_file_wait(filp, cmd, file_lock); + WARN_ON_ONCE(error); + error = -EBADF; + } } - out: locks_free_lock(file_lock); return error; @@ -2089,7 +2091,6 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, goto out; } -again: error = flock64_to_posix_lock(filp, file_lock, &flock); if (error) goto out; @@ -2120,14 +2121,22 @@ again: * Attempt to detect a close/fcntl race and recover by * releasing the lock that was just acquired. */ - spin_lock(¤t->files->file_lock); - f = fcheck(fd); - spin_unlock(¤t->files->file_lock); - if (!error && f != filp && flock.l_type != F_UNLCK) { - flock.l_type = F_UNLCK; - goto again; + if (!error && file_lock->fl_type != F_UNLCK) { + /* + * We need that spin_lock here - it prevents reordering between + * update of inode->i_flock and check for it done in + * close(). rcu_read_lock() wouldn't do. + */ + spin_lock(¤t->files->file_lock); + f = fcheck(fd); + spin_unlock(¤t->files->file_lock); + if (f != filp) { + file_lock->fl_type = F_UNLCK; + error = do_lock_file_wait(filp, cmd, file_lock); + WARN_ON_ONCE(error); + error = -EBADF; + } } - out: locks_free_lock(file_lock); return error; -- 2.7.2