From patchwork Thu Apr 16 05:31:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 11492311 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DAE2A913 for ; Thu, 16 Apr 2020 05:32:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C338920857 for ; Thu, 16 Apr 2020 05:32:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="YibKIVsw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406625AbgDPFcQ (ORCPT ); Thu, 16 Apr 2020 01:32:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2406396AbgDPFcN (ORCPT ); Thu, 16 Apr 2020 01:32:13 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBB57C061A41; Wed, 15 Apr 2020 22:32:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=067wQeP/XsQZz7g9kDshfnJ5VToeesdhipVsn0gNrtY=; b=YibKIVswQ5pUBnsRMM6VfjsvQ8 g4PkIfoEwbBcSGD1mLF+cQGk90fOYWm0fTmHuUNjn6GTpQXyIWjV4KoR08kg9crGiaO89xCJvC/0j tyOiapEMb0oHb8sAiYMe6l55EZ2juDaT/0ZiN7o50JEV4RaKsxdjS1w5hhsuNy4H3Ua1KZ+QsQ76i h9udkToejdlmgZPNEn3mYobJY6O79O2dzot1xmq7C1Asm8KAZ9OyZGJMK2joYCbz7VGjYLzEzOGc1 jqkNWWfMFa/3SegvAOVFQRy65e82bVNzbrubo/KsI2n28M9QW1nzS6EMiyZ0NApYCYFDbesPY5sci iWGGTEsg==; Received: from [2001:4bb8:184:4aa1:c70:4a89:bc61:2] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOx8C-0003dn-CA; Thu, 16 Apr 2020 05:32:08 +0000 From: Christoph Hellwig To: Linus Torvalds , Andrew Morton Cc: Al Viro , Felix Kuehling , Alex Deucher , Zhenyu Wang , Zhi Wang , Felipe Balbi , "Michael S. Tsirkin" , Jason Wang , Jens Axboe , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-usb@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 3/3] kernel: set USER_DS in kthread_use_mm Date: Thu, 16 Apr 2020 07:31:58 +0200 Message-Id: <20200416053158.586887-4-hch@lst.de> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200416053158.586887-1-hch@lst.de> References: <20200416053158.586887-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Some architectures like arm64 and s390 require USER_DS to be set for kernel threads to access user address space, which is the whole purpose of kthread_use_mm, but other like x86 don't. That has lead to a huge mess where some callers are fixed up once they are tested on said architectures, while others linger around and yet other like io_uring try to do "clever" optimizations for what usually is just a trivial asignment to a member in the thread_struct for most architectures. Make kthread_use_mm set USER_DS, and kthread_unuse_mm restore to the previous value instead. Signed-off-by: Christoph Hellwig Acked-by: Michael S. Tsirkin [vhost] Acked-by: Greg Kroah-Hartman [usb] --- drivers/usb/gadget/function/f_fs.c | 4 ---- drivers/vhost/vhost.c | 3 --- fs/io-wq.c | 8 ++------ fs/io_uring.c | 4 ---- kernel/kthread.c | 6 ++++++ 5 files changed, 8 insertions(+), 17 deletions(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index d9e48bd7c692..a1198f4c527c 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -824,13 +824,9 @@ static void ffs_user_copy_worker(struct work_struct *work) bool kiocb_has_eventfd = io_data->kiocb->ki_flags & IOCB_EVENTFD; if (io_data->read && ret > 0) { - mm_segment_t oldfs = get_fs(); - - set_fs(USER_DS); kthread_use_mm(io_data->mm); ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data); kthread_unuse_mm(io_data->mm); - set_fs(oldfs); } io_data->kiocb->ki_complete(io_data->kiocb, ret, ret); diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 17d598e74780..b2abfbdf3cb2 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -329,9 +329,7 @@ static int vhost_worker(void *data) struct vhost_dev *dev = data; struct vhost_work *work, *work_next; struct llist_node *node; - mm_segment_t oldfs = get_fs(); - set_fs(USER_DS); kthread_use_mm(dev->mm); for (;;) { @@ -361,7 +359,6 @@ static int vhost_worker(void *data) } } kthread_unuse_mm(dev->mm); - set_fs(oldfs); return 0; } diff --git a/fs/io-wq.c b/fs/io-wq.c index 748621f7391e..a5e90ac39e4d 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -169,7 +169,6 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker) dropped_lock = true; } __set_current_state(TASK_RUNNING); - set_fs(KERNEL_DS); kthread_unuse_mm(worker->mm); mmput(worker->mm); worker->mm = NULL; @@ -421,14 +420,11 @@ static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work) mmput(worker->mm); worker->mm = NULL; } - if (!work->mm) { - set_fs(KERNEL_DS); + if (!work->mm) return; - } + if (mmget_not_zero(work->mm)) { kthread_use_mm(work->mm); - if (!worker->mm) - set_fs(USER_DS); worker->mm = work->mm; /* hang on to this mm */ work->mm = NULL; diff --git a/fs/io_uring.c b/fs/io_uring.c index 8a8148512da7..40f90b98a18a 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5908,15 +5908,12 @@ static int io_sq_thread(void *data) struct io_ring_ctx *ctx = data; struct mm_struct *cur_mm = NULL; const struct cred *old_cred; - mm_segment_t old_fs; DEFINE_WAIT(wait); unsigned long timeout; int ret = 0; complete(&ctx->completions[1]); - old_fs = get_fs(); - set_fs(USER_DS); old_cred = override_creds(ctx->creds); timeout = jiffies + ctx->sq_thread_idle; @@ -6023,7 +6020,6 @@ static int io_sq_thread(void *data) if (current->task_works) task_work_run(); - set_fs(old_fs); if (cur_mm) { kthread_unuse_mm(cur_mm); mmput(cur_mm); diff --git a/kernel/kthread.c b/kernel/kthread.c index 8ed4b4fbec7c..86357cd38eb2 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -52,6 +52,7 @@ struct kthread { unsigned long flags; unsigned int cpu; void *data; + mm_segment_t oldfs; struct completion parked; struct completion exited; #ifdef CONFIG_BLK_CGROUP @@ -1235,6 +1236,9 @@ void kthread_use_mm(struct mm_struct *mm) if (active_mm != mm) mmdrop(active_mm); + + to_kthread(tsk)->oldfs = get_fs(); + set_fs(USER_DS); } EXPORT_SYMBOL_GPL(kthread_use_mm); @@ -1249,6 +1253,8 @@ void kthread_unuse_mm(struct mm_struct *mm) WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); WARN_ON_ONCE(!tsk->mm); + set_fs(to_kthread(tsk)->oldfs); + task_lock(tsk); sync_mm_rss(mm); tsk->mm = NULL;