From nobody Tue Sep 23 22:09:20 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1752746001062255.77128216387678; Thu, 17 Jul 2025 02:53:21 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ucLG9-0003Vu-PP; Thu, 17 Jul 2025 05:50:43 -0400 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 1ucL0Y-0001rZ-GA; Thu, 17 Jul 2025 05:34:35 -0400 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ucL0W-0001oW-ME; Thu, 17 Jul 2025 05:34:30 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 84EB9137CED; Thu, 17 Jul 2025 12:34:04 +0300 (MSK) Received: from think4mjt.origo (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id 695D72491E7; Thu, 17 Jul 2025 12:34:12 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Geoffrey Thomas , Richard Henderson , Michael Tokarev Subject: [Stable-10.0.3 45/65] linux-user: Hold the fd-trans lock across fork Date: Thu, 17 Jul 2025 12:33:41 +0300 Message-ID: <20250717093412.728292-6-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1752746002952116600 Content-Type: text/plain; charset="utf-8" From: Geoffrey Thomas If another thread is holding target_fd_trans_lock during a fork, then the lock becomes permanently locked in the child and the emulator deadlocks at the next interaction with the fd-trans table. As with other locks, acquire the lock in fork_start() and release it in fork_end(). Cc: qemu-stable@nongnu.org Signed-off-by: Geoffrey Thomas Fixes: c093364f4d91 "fd-trans: Fix race condition on reallocation of the tr= anslation table." Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2846 Buglink: https://github.com/astral-sh/uv/issues/6105 Reviewed-by: Richard Henderson Signed-off-by: Richard Henderson Message-ID: <20250314124742.4965-1-geofft@ldpreload.com> (cherry picked from commit e4e839b2eeea5745c48ce47144c7842eb7cd455f) Signed-off-by: Michael Tokarev diff --git a/linux-user/fd-trans.h b/linux-user/fd-trans.h index 910faaf237..e14f96059c 100644 --- a/linux-user/fd-trans.h +++ b/linux-user/fd-trans.h @@ -36,6 +36,16 @@ static inline void fd_trans_init(void) qemu_mutex_init(&target_fd_trans_lock); } =20 +static inline void fd_trans_prefork(void) +{ + qemu_mutex_lock(&target_fd_trans_lock); +} + +static inline void fd_trans_postfork(void) +{ + qemu_mutex_unlock(&target_fd_trans_lock); +} + static inline TargetFdDataFunc fd_trans_target_to_host_data(int fd) { if (fd < 0) { diff --git a/linux-user/main.c b/linux-user/main.c index e2ec5970be..2cd867491b 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -149,12 +149,14 @@ void fork_start(void) cpu_list_lock(); qemu_plugin_user_prefork_lock(); gdbserver_fork_start(); + fd_trans_prefork(); } =20 void fork_end(pid_t pid) { bool child =3D pid =3D=3D 0; =20 + fd_trans_postfork(); qemu_plugin_user_postfork(child); mmap_fork_end(child); if (child) { --=20 2.47.2