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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 39F13CCFA03 for ; Tue, 4 Nov 2025 02:30:42 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vG6nw-0006y7-97; Mon, 03 Nov 2025 21:29:52 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vG6nu-0006x6-7j for qemu-devel@nongnu.org; Mon, 03 Nov 2025 21:29:50 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vG6ns-0003tH-Ml for qemu-devel@nongnu.org; Mon, 03 Nov 2025 21:29:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762223387; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=A4eBsQ02JlkSujwNhtGdbX6FLAtNyGzdAxZ9dBj/Igk=; b=YB6JoYfaywuEa2tN7S4xkNo83yRR6P9nD3CcKqRxMfQMUEzfG88KsrHePTbzZV0I3AX0+Q zHccZ9Sgnwyy+HCEMyrhzt6Ylv83edFil+R6OHIvXzNcccTw/POA4CwW3BOTQD6nRZC3cW Bz0dHNcbBCOWq0daulZniA32shCtyS0= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-478-Fdv-DBgTP4KDefbXmchejA-1; Mon, 03 Nov 2025 21:29:44 -0500 X-MC-Unique: Fdv-DBgTP4KDefbXmchejA-1 X-Mimecast-MFC-AGG-ID: Fdv-DBgTP4KDefbXmchejA_1762223383 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DDE301800245; Tue, 4 Nov 2025 02:29:42 +0000 (UTC) Received: from localhost (unknown [10.2.16.6]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 104E21956056; Tue, 4 Nov 2025 02:29:41 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , Kevin Wolf , eblake@redhat.com, Hanna Czenczek , qemu-block@nongnu.org, Paolo Bonzini , Fam Zheng , hibriansong@gmail.com Subject: [PATCH v6 02/15] aio-posix: fix fdmon-io_uring.c timeout stack variable lifetime Date: Mon, 3 Nov 2025 21:29:20 -0500 Message-ID: <20251104022933.618123-3-stefanha@redhat.com> In-Reply-To: <20251104022933.618123-1-stefanha@redhat.com> References: <20251104022933.618123-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org io_uring_prep_timeout() stashes a pointer to the timespec struct rather than copying its fields. That means the struct must live until after the SQE has been submitted by io_uring_enter(2). add_timeout_sqe() violates this constraint because the SQE is not submitted within the function. Inline add_timeout_sqe() into fdmon_io_uring_wait() so that the struct lives at least as long as io_uring_enter(2). This fixes random hangs (bogus timeout values) when the kernel loads undefined timespec struct values from userspace after the original struct on the stack has been destroyed. Reported-by: Kevin Wolf Signed-off-by: Stefan Hajnoczi --- util/fdmon-io_uring.c | 27 ++++++++++++--------------- 1 file changed, 12 insertions(+), 15 deletions(-) diff --git a/util/fdmon-io_uring.c b/util/fdmon-io_uring.c index ad89160f31..b64ce42513 100644 --- a/util/fdmon-io_uring.c +++ b/util/fdmon-io_uring.c @@ -188,20 +188,6 @@ static void add_poll_remove_sqe(AioContext *ctx, AioHandler *node) io_uring_sqe_set_data(sqe, NULL); } -/* Add a timeout that self-cancels when another cqe becomes ready */ -static void add_timeout_sqe(AioContext *ctx, int64_t ns) -{ - struct io_uring_sqe *sqe; - struct __kernel_timespec ts = { - .tv_sec = ns / NANOSECONDS_PER_SECOND, - .tv_nsec = ns % NANOSECONDS_PER_SECOND, - }; - - sqe = get_sqe(ctx); - io_uring_prep_timeout(sqe, &ts, 1, 0); - io_uring_sqe_set_data(sqe, NULL); -} - /* Add sqes from ctx->submit_list for submission */ static void fill_sq_ring(AioContext *ctx) { @@ -291,13 +277,24 @@ static int process_cq_ring(AioContext *ctx, AioHandlerList *ready_list) static int fdmon_io_uring_wait(AioContext *ctx, AioHandlerList *ready_list, int64_t timeout) { + struct __kernel_timespec ts; unsigned wait_nr = 1; /* block until at least one cqe is ready */ int ret; if (timeout == 0) { wait_nr = 0; /* non-blocking */ } else if (timeout > 0) { - add_timeout_sqe(ctx, timeout); + /* Add a timeout that self-cancels when another cqe becomes ready */ + struct io_uring_sqe *sqe; + + ts = (struct __kernel_timespec){ + .tv_sec = timeout / NANOSECONDS_PER_SECOND, + .tv_nsec = timeout % NANOSECONDS_PER_SECOND, + }; + + sqe = get_sqe(ctx); + io_uring_prep_timeout(sqe, &ts, 1, 0); + io_uring_sqe_set_data(sqe, NULL); } fill_sq_ring(ctx); -- 2.51.1