From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753950AbcAHCWf (ORCPT ); Thu, 7 Jan 2016 21:22:35 -0500 Received: from mail-qg0-f44.google.com ([209.85.192.44]:34600 "EHLO mail-qg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753109AbcAHCWd (ORCPT ); Thu, 7 Jan 2016 21:22:33 -0500 From: Jeff Layton X-Google-Original-From: Jeff Layton To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Dmitry Vyukov , "J. Bruce Fields" , Alexander Viro , syzkaller , Kostya Serebryany , Alexander Potapenko , Sasha Levin , Eric Dumazet Subject: [PATCH] locks: fix unlock when fcntl_setlk races with a close Date: Thu, 7 Jan 2016 21:22:22 -0500 Message-Id: <1452219742-18507-1-git-send-email-jeff.layton@primarydata.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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: Reported-by: Dmitry Vyukov Signed-off-by: Jeff Layton --- fs/locks.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 593dca300b29..0db640e4ced4 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -2181,7 +2181,6 @@ 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; @@ -2231,9 +2230,11 @@ again: 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 && f != filp && file_lock->fl_type != F_UNLCK) { + file_lock->fl_type = F_UNLCK; + error = do_lock_file_wait(filp, cmd, file_lock); + WARN_ON_ONCE(error); + error = -EBADF; } out: @@ -2321,7 +2322,6 @@ 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; @@ -2366,11 +2366,12 @@ again: 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 && f != filp && file_lock->fl_type != F_UNLCK) { + 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; -- 2.5.0