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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9338C433FE for ; Thu, 13 Oct 2022 00:27:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229965AbiJMA1F (ORCPT ); Wed, 12 Oct 2022 20:27:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231234AbiJMAYG (ORCPT ); Wed, 12 Oct 2022 20:24:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E6DF5FFB; Wed, 12 Oct 2022 17:22:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7B21461662; Thu, 13 Oct 2022 00:22:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BBD4AC433D6; Thu, 13 Oct 2022 00:22:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665620559; bh=XTvP40iNi0+Eiwq3T0oEZhoWupUubEI8vDr3+gwG8iI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RCMYEj16aIEmWQd8itssfAGXhLJciRw/zsZrAiyiFwVaaihIb3gRfidxq0Q1Z1l/l Ge7W9S4pppLrGdJIy+E603havNMOct8EkLtd3L7NwcqoexVwyAtDVbYSfuHRiU9n+v rFDdzEzNk1rHr+D/gS3rcy9RWaF2OcbzHtANEg3f68I9pe9tOOUbS4Pn21iYm9Nddj lFVGwTEwGupxn9XfEVIRbmFfCZvx7pzIOsn2hzlcqJhRBgDL318BDA8tvfal0e1tLG 5lpqmVowzz/kfd98jDIhwayV09yfzbpA3GmvAoFSWGvtcRxitfjj+fFsHd3QnbF4Gk 7+Vcq9ZgtEPEA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Dylan Yudaken , Jens Axboe , Sasha Levin , viro@zeniv.linux.org.uk, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 27/47] eventfd: guard wake_up in eventfd fs calls as well Date: Wed, 12 Oct 2022 20:21:02 -0400 Message-Id: <20221013002124.1894077-27-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221013002124.1894077-1-sashal@kernel.org> References: <20221013002124.1894077-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dylan Yudaken [ Upstream commit 9f0deaa12d832f488500a5afe9b912e9b3cfc432 ] Guard wakeups that the user can trigger, and that may end up triggering a call back into eventfd_signal. This is in addition to the current approach that only guards in eventfd_signal. Rename in_eventfd_signal -> in_eventfd at the same time to reflect this. Without this there would be a deadlock in the following code using libaio: int main() { struct io_context *ctx = NULL; struct iocb iocb; struct iocb *iocbs[] = { &iocb }; int evfd; uint64_t val = 1; evfd = eventfd(0, EFD_CLOEXEC); assert(!io_setup(2, &ctx)); io_prep_poll(&iocb, evfd, POLLIN); io_set_eventfd(&iocb, evfd); assert(1 == io_submit(ctx, 1, iocbs)); write(evfd, &val, 8); } Signed-off-by: Dylan Yudaken Reviewed-by: Jens Axboe Link: https://lore.kernel.org/r/20220816135959.1490641-1-dylany@fb.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- fs/eventfd.c | 10 +++++++--- include/linux/eventfd.h | 2 +- include/linux/sched.h | 2 +- 3 files changed, 9 insertions(+), 5 deletions(-) diff --git a/fs/eventfd.c b/fs/eventfd.c index 3627dd7d25db..c0ffee99ad23 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -69,17 +69,17 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n) * it returns false, the eventfd_signal() call should be deferred to a * safe context. */ - if (WARN_ON_ONCE(current->in_eventfd_signal)) + if (WARN_ON_ONCE(current->in_eventfd)) return 0; spin_lock_irqsave(&ctx->wqh.lock, flags); - current->in_eventfd_signal = 1; + current->in_eventfd = 1; if (ULLONG_MAX - ctx->count < n) n = ULLONG_MAX - ctx->count; ctx->count += n; if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, EPOLLIN); - current->in_eventfd_signal = 0; + current->in_eventfd = 0; spin_unlock_irqrestore(&ctx->wqh.lock, flags); return n; @@ -253,8 +253,10 @@ static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to) __set_current_state(TASK_RUNNING); } eventfd_ctx_do_read(ctx, &ucnt); + current->in_eventfd = 1; if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, EPOLLOUT); + current->in_eventfd = 0; spin_unlock_irq(&ctx->wqh.lock); if (unlikely(copy_to_iter(&ucnt, sizeof(ucnt), to) != sizeof(ucnt))) return -EFAULT; @@ -301,8 +303,10 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c } if (likely(res > 0)) { ctx->count += ucnt; + current->in_eventfd = 1; if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, EPOLLIN); + current->in_eventfd = 0; } spin_unlock_irq(&ctx->wqh.lock); diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h index 305d5f19093b..30eb30d6909b 100644 --- a/include/linux/eventfd.h +++ b/include/linux/eventfd.h @@ -46,7 +46,7 @@ void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt); static inline bool eventfd_signal_allowed(void) { - return !current->in_eventfd_signal; + return !current->in_eventfd; } #else /* CONFIG_EVENTFD */ diff --git a/include/linux/sched.h b/include/linux/sched.h index dcba347cbffa..e418935f8db6 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -933,7 +933,7 @@ struct task_struct { #endif #ifdef CONFIG_EVENTFD /* Recursion prevention for eventfd_signal() */ - unsigned in_eventfd_signal:1; + unsigned in_eventfd:1; #endif unsigned long atomic_flags; /* Flags requiring atomic access. */ -- 2.35.1