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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 AA888C4338F for ; Mon, 16 Aug 2021 12:13:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E38F63244 for ; Mon, 16 Aug 2021 12:13:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229884AbhHPMNj (ORCPT ); Mon, 16 Aug 2021 08:13:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:38430 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229836AbhHPMNj (ORCPT ); Mon, 16 Aug 2021 08:13:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2A14063249; Mon, 16 Aug 2021 12:13:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1629115987; bh=GNyx2P9hNeHot/fpj6/bCc+MMdOx2CQBkka4VU/iO2g=; h=Subject:To:Cc:From:Date:From; b=sW0Z9pH0b4ytLzb4AWOoMkPT5zy7rNiEx5nFoavado7AVAoT3uf2sd3NoZoceTQYk 7vPDd9wHWFe9xxSVqVkDACef/VWTIybQj1ODZv837Kbv/PpwdFaLqV+iWnY9Ddhlkk Huk0D/9IQfrxfq86+fSgYNsFhk5yl+7RoK8dXXWA= Subject: FAILED: patch "[PATCH] io_uring: Use WRITE_ONCE() when writing to sq_flags" failed to apply to 5.4-stable tree To: namit@vmware.com, asml.silence@gmail.com, axboe@kernel.dk Cc: From: Date: Mon, 16 Aug 2021 14:13:05 +0200 Message-ID: <1629115985118160@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 20c0b380f971e7d48f5d978bc27d827f7eabb21a Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Sat, 7 Aug 2021 17:13:42 -0700 Subject: [PATCH] io_uring: Use WRITE_ONCE() when writing to sq_flags The compiler should be forbidden from any strange optimization for async writes to user visible data-structures. Without proper protection, the compiler can cause write-tearing or invent writes that would confuse the userspace. However, there are writes to sq_flags which are not protected by WRITE_ONCE(). Use WRITE_ONCE() for these writes. This is purely a theoretical issue. Presumably, any compiler is very unlikely to do such optimizations. Fixes: 75b28affdd6a ("io_uring: allocate the two rings together") Cc: Jens Axboe Cc: Pavel Begunkov Signed-off-by: Nadav Amit Link: https://lore.kernel.org/r/20210808001342.964634-3-namit@vmware.com Signed-off-by: Jens Axboe diff --git a/fs/io_uring.c b/fs/io_uring.c index 1093df3977b8..ca064486cb41 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1500,7 +1500,8 @@ static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force) all_flushed = list_empty(&ctx->cq_overflow_list); if (all_flushed) { clear_bit(0, &ctx->check_cq_overflow); - ctx->rings->sq_flags &= ~IORING_SQ_CQ_OVERFLOW; + WRITE_ONCE(ctx->rings->sq_flags, + ctx->rings->sq_flags & ~IORING_SQ_CQ_OVERFLOW); } if (posted) @@ -1579,7 +1580,9 @@ static bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data, } if (list_empty(&ctx->cq_overflow_list)) { set_bit(0, &ctx->check_cq_overflow); - ctx->rings->sq_flags |= IORING_SQ_CQ_OVERFLOW; + WRITE_ONCE(ctx->rings->sq_flags, + ctx->rings->sq_flags | IORING_SQ_CQ_OVERFLOW); + } ocqe->cqe.user_data = user_data; ocqe->cqe.res = res; @@ -6804,14 +6807,16 @@ static inline void io_ring_set_wakeup_flag(struct io_ring_ctx *ctx) { /* Tell userspace we may need a wakeup call */ spin_lock_irq(&ctx->completion_lock); - ctx->rings->sq_flags |= IORING_SQ_NEED_WAKEUP; + WRITE_ONCE(ctx->rings->sq_flags, + ctx->rings->sq_flags | IORING_SQ_NEED_WAKEUP); spin_unlock_irq(&ctx->completion_lock); } static inline void io_ring_clear_wakeup_flag(struct io_ring_ctx *ctx) { spin_lock_irq(&ctx->completion_lock); - ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP; + WRITE_ONCE(ctx->rings->sq_flags, + ctx->rings->sq_flags & ~IORING_SQ_NEED_WAKEUP); spin_unlock_irq(&ctx->completion_lock); }