From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:37584 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732772AbeKLISZ (ORCPT ); Mon, 12 Nov 2018 03:18:25 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Christoph Hellwig , Andrea Arcangeli , Andrew Morton , Linus Torvalds Subject: [PATCH 4.19 249/361] userfaultfd: disable irqs when taking the waitqueue lock Date: Sun, 11 Nov 2018 14:19:56 -0800 Message-Id: <20181111221653.034748085@linuxfoundation.org> In-Reply-To: <20181111221619.915519183@linuxfoundation.org> References: <20181111221619.915519183@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christoph Hellwig commit ae62c16e105a869524afcf8a07ee85c5ae5d0479 upstream. userfaultfd contains howe-grown locking of the waitqueue lock, and does not disable interrupts. This relies on the fact that no one else takes it from interrupt context and violates an invariat of the normal waitqueue locking scheme. With aio poll it is easy to trigger other locks that disable interrupts (or are called from interrupt context). Link: http://lkml.kernel.org/r/20181018154101.18750-1-hch@lst.de Signed-off-by: Christoph Hellwig Reviewed-by: Andrea Arcangeli Reviewed-by: Andrew Morton Cc: [4.19.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/userfaultfd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1026,7 +1026,7 @@ static ssize_t userfaultfd_ctx_read(stru struct userfaultfd_ctx *fork_nctx = NULL; /* always take the fd_wqh lock before the fault_pending_wqh lock */ - spin_lock(&ctx->fd_wqh.lock); + spin_lock_irq(&ctx->fd_wqh.lock); __add_wait_queue(&ctx->fd_wqh, &wait); for (;;) { set_current_state(TASK_INTERRUPTIBLE); @@ -1112,13 +1112,13 @@ static ssize_t userfaultfd_ctx_read(stru ret = -EAGAIN; break; } - spin_unlock(&ctx->fd_wqh.lock); + spin_unlock_irq(&ctx->fd_wqh.lock); schedule(); - spin_lock(&ctx->fd_wqh.lock); + spin_lock_irq(&ctx->fd_wqh.lock); } __remove_wait_queue(&ctx->fd_wqh, &wait); __set_current_state(TASK_RUNNING); - spin_unlock(&ctx->fd_wqh.lock); + spin_unlock_irq(&ctx->fd_wqh.lock); if (!ret && msg->event == UFFD_EVENT_FORK) { ret = resolve_userfault_fork(ctx, fork_nctx, msg);