From nobody Thu Dec 18 04:15:50 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 1752749890927166.75477435460039; Thu, 17 Jul 2025 03:58:10 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ucMGM-0007Jt-Va; Thu, 17 Jul 2025 06:54:55 -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 1ucMGF-00079v-Lb; Thu, 17 Jul 2025 06:54:50 -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 1ucMGD-00036s-AM; Thu, 17 Jul 2025 06:54:47 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id C179F137E1C; Thu, 17 Jul 2025 13:54:34 +0300 (MSK) Received: from think4mjt.origo (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id BD21F249266; Thu, 17 Jul 2025 13:54:42 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Geoffrey Thomas , Richard Henderson , Michael Tokarev Subject: [Stable-7.2.19 16/26] linux-user: Hold the fd-trans lock across fork Date: Thu, 17 Jul 2025 13:54:30 +0300 Message-ID: <20250717105442.735202-1-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: 1752749891571116600 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) (Mjt: adjust context in linux/main.c for 7.2) 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 a17fed045b..3572d95e69 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -143,10 +143,12 @@ void fork_start(void) mmap_fork_start(); cpu_list_lock(); qemu_plugin_user_prefork_lock(); + fd_trans_prefork(); } =20 void fork_end(int child) { + fd_trans_postfork(); qemu_plugin_user_postfork(child); mmap_fork_end(child); if (child) { --=20 2.47.2