From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 708EAFC6195 for ; Fri, 8 Nov 2019 18:56:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E37C21D7B for ; Fri, 8 Nov 2019 18:56:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573239386; bh=QQnacO8XTYFkVvC98SZyoS78neMj+cLplwvBEkW6pO8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=nZDgKGuGmMUu+fCNswONptyi1xe7z6+NZqWxsBUdrT8CNuvPoJ7ULxRiXhPHe9LU3 KHcS2LqFKJ5VBaPL5pWSnjf0sEGR5L0Uc1P4tgzNmO1BJ8W2LipmD6rCELt2Tereyj 4u3WyPh7ilmQOnzxHfYtOYukmmmVMV7MVQLZJCoc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388229AbfKHS4Z (ORCPT ); Fri, 8 Nov 2019 13:56:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:53770 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388064AbfKHS4M (ORCPT ); Fri, 8 Nov 2019 13:56:12 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D92CF21D7B; Fri, 8 Nov 2019 18:56:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573239371; bh=QQnacO8XTYFkVvC98SZyoS78neMj+cLplwvBEkW6pO8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gi7KSYmZ92TAw6kcdDMPq793qvS7059jFB7gNZb26oCYzaNY5YqBXULCzPho5c2io v4Fg1yRBJpw8+1CwL4yFMbFi2jC+u8UdIw5JIB/KlRw75qxPQ/OQO5TrAJgcT8RL4R o2nOB+NGORws0Mq+z89Y40hpqz6a2HlOzJ+rbV+o= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dave Wysochanski , Ronnie Sahlberg , Pavel Shilovsky , Sasha Levin Subject: [PATCH 4.9 17/34] cifs: Fix cifsInodeInfo lock_sem deadlock when reconnect occurs Date: Fri, 8 Nov 2019 19:50:24 +0100 Message-Id: <20191108174637.779336809@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191108174618.266472504@linuxfoundation.org> References: <20191108174618.266472504@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Wysochanski [ Upstream commit d46b0da7a33dd8c99d969834f682267a45444ab3 ] There's a deadlock that is possible and can easily be seen with a test where multiple readers open/read/close of the same file and a disruption occurs causing reconnect. The deadlock is due a reader thread inside cifs_strict_readv calling down_read and obtaining lock_sem, and then after reconnect inside cifs_reopen_file calling down_read a second time. If in between the two down_read calls, a down_write comes from another process, deadlock occurs. CPU0 CPU1 ---- ---- cifs_strict_readv() down_read(&cifsi->lock_sem); _cifsFileInfo_put OR cifs_new_fileinfo down_write(&cifsi->lock_sem); cifs_reopen_file() down_read(&cifsi->lock_sem); Fix the above by changing all down_write(lock_sem) calls to down_write_trylock(lock_sem)/msleep() loop, which in turn makes the second down_read call benign since it will never block behind the writer while holding lock_sem. Signed-off-by: Dave Wysochanski Suggested-by: Ronnie Sahlberg Reviewed--by: Ronnie Sahlberg Reviewed-by: Pavel Shilovsky Signed-off-by: Sasha Levin --- fs/cifs/cifsglob.h | 5 +++++ fs/cifs/cifsproto.h | 1 + fs/cifs/file.c | 23 +++++++++++++++-------- fs/cifs/smb2file.c | 2 +- 4 files changed, 22 insertions(+), 9 deletions(-) diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 5367b684c1f74..7ae21ad420fbf 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1178,6 +1178,11 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file); struct cifsInodeInfo { bool can_cache_brlcks; struct list_head llist; /* locks helb by this inode */ + /* + * NOTE: Some code paths call down_read(lock_sem) twice, so + * we must always use use cifs_down_write() instead of down_write() + * for this semaphore to avoid deadlocks. + */ struct rw_semaphore lock_sem; /* protect the fields above */ /* BB add in lists for dirty pages i.e. write caching info for oplock */ struct list_head openFileList; diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h index cd8025a249bba..cdf244df91c25 100644 --- a/fs/cifs/cifsproto.h +++ b/fs/cifs/cifsproto.h @@ -138,6 +138,7 @@ extern int cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock, const unsigned int xid); extern int cifs_push_mandatory_locks(struct cifsFileInfo *cfile); +extern void cifs_down_write(struct rw_semaphore *sem); extern struct cifsFileInfo *cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, struct tcon_link *tlink, diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 3504ef015493b..1c3f262d9c4d4 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -280,6 +280,13 @@ cifs_has_mand_locks(struct cifsInodeInfo *cinode) return has_locks; } +void +cifs_down_write(struct rw_semaphore *sem) +{ + while (!down_write_trylock(sem)) + msleep(10); +} + struct cifsFileInfo * cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, struct tcon_link *tlink, __u32 oplock) @@ -305,7 +312,7 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, INIT_LIST_HEAD(&fdlocks->locks); fdlocks->cfile = cfile; cfile->llist = fdlocks; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_add(&fdlocks->llist, &cinode->llist); up_write(&cinode->lock_sem); @@ -457,7 +464,7 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file, bool wait_oplock_handler) * Delete any outstanding lock records. We'll lose them when the file * is closed anyway. */ - down_write(&cifsi->lock_sem); + cifs_down_write(&cifsi->lock_sem); list_for_each_entry_safe(li, tmp, &cifs_file->llist->locks, llist) { list_del(&li->llist); cifs_del_lock_waiters(li); @@ -1011,7 +1018,7 @@ static void cifs_lock_add(struct cifsFileInfo *cfile, struct cifsLockInfo *lock) { struct cifsInodeInfo *cinode = CIFS_I(d_inode(cfile->dentry)); - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_add_tail(&lock->llist, &cfile->llist->locks); up_write(&cinode->lock_sem); } @@ -1033,7 +1040,7 @@ cifs_lock_add_if(struct cifsFileInfo *cfile, struct cifsLockInfo *lock, try_again: exist = false; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); exist = cifs_find_lock_conflict(cfile, lock->offset, lock->length, lock->type, &conf_lock, CIFS_LOCK_OP); @@ -1055,7 +1062,7 @@ cifs_lock_add_if(struct cifsFileInfo *cfile, struct cifsLockInfo *lock, (lock->blist.next == &lock->blist)); if (!rc) goto try_again; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_del_init(&lock->blist); } @@ -1108,7 +1115,7 @@ cifs_posix_lock_set(struct file *file, struct file_lock *flock) return rc; try_again: - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); if (!cinode->can_cache_brlcks) { up_write(&cinode->lock_sem); return rc; @@ -1312,7 +1319,7 @@ cifs_push_locks(struct cifsFileInfo *cfile) int rc = 0; /* we are going to update can_cache_brlcks here - need a write access */ - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); if (!cinode->can_cache_brlcks) { up_write(&cinode->lock_sem); return rc; @@ -1501,7 +1508,7 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock, if (!buf) return -ENOMEM; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); for (i = 0; i < 2; i++) { cur = buf; num = 0; diff --git a/fs/cifs/smb2file.c b/fs/cifs/smb2file.c index dee5250701deb..41f1a5dd33a53 100644 --- a/fs/cifs/smb2file.c +++ b/fs/cifs/smb2file.c @@ -138,7 +138,7 @@ smb2_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock, cur = buf; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_for_each_entry_safe(li, tmp, &cfile->llist->locks, llist) { if (flock->fl_start > li->offset || (flock->fl_start + length) < -- 2.20.1