From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793208075; b=TRzy2cF+ahmp5h97glJeLfFU+0PHBpOT4s5KhBrPtdwMRgyJWA+29qOsDEOWaMMfnmmH qMeEQsnbVnlEXgDkS2ATeIPFo3D+RqaUe3kZN7ppusTkdzNXUm8Qhk7pQwn/M1LOL/7in K0mXwuESIbe7gHhBkDLC/OhL+qsooaAbQE6S2bMSvmLV44IRK7EmezKOSGFLaBzu/LV40 O+JYiQoGu64mokBd6QNnYaGno/1zTCWdwT7jcScOIRuFCzQ+HQOGMWlRHfw/BYRAsst82 7apUTHoEGX77b5TCaWDZgIwRtYfgxNRifq7qoRxLqlobloaJpFlQ2FwxWnDJ0zmZTtA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793208075; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=r0yt+9PlPIDL0+MrTEXzfTyUgAmcxwfwkp8ROWUjGlg=; b=ldCb6NogcRqutYzIwcM65l9GztzvLMQ2723YjTRY85fzYehFLh31OallGLe/izxFiV+0 UkujVQ3MCN9CxOEk3RSS5aQp0060BaYmKgx8zuW5iCwEZWbYfofPef3gaxCp8ndM4ALZ9 YYE2KVyKFnR4gtDkd8YZFcwhDyAmSLbIW30iirpGzYEGY9wUyfJ170j5FtV9Qb1jOHhnX 2k1DOd5xwePYs1QdiJ0JtsNeVWU1wRRL8dr5iOOMs07FM8NIhSgOyF61KJL5MnY+Yc3Wt VN1bujZvMdzZzAzmYsDoBlfOVh8Qgh6Z4QBcusTOJ/kRyt1esjYtsGUPUqVF3+ghlzA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=JbYKvetf; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B340606A31D; Wed, 28 Oct 2026 17:21:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=JbYKvetf Received: by smtp.kernel.org (Postfix) with ESMTPSA id 795951F01825; Wed, 28 Oct 2026 17:21:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793208075; bh=r0yt+9PlPIDL0+MrTEXzfTyUgAmcxwfwkp8ROWUjGlg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JbYKvetfJir06GrGMon+oOrPO2uMG4+EMhwxT+8/9K/NY6vqq8kmJdP+q2V4SOEmn KiMnLOjYHHDHijXHPnKGV/2zYreQeXrWeFnsLSW2VWKAwZJNJsxvzZfj93DCfTs2gJ 8aF4OePi+khbJxKKIF/24LHejJB+X4MeUe+JTgdY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Oleg Nesterov , "Christian Brauner (Amutable)" Subject: [PATCH 6.12 240/247] coredump: hold RCU while releasing parked threads Date: Wed, 28 Oct 2026 18:00:43 +0100 Message-ID: <20261028165953.105996139@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165947.349197979@linuxfoundation.org> References: <20261028165947.349197979@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner commit 61d58591aa0188bf2463e263962256316ff8b576 upstream. coredump_finish() releases the parked threads by clearing ->task in their core_thread entry and calling wake_up_process() on each of them. It does that without holding a reference on the task and without being inside rcu. But calling wake_up_process(task) without rcu here isn't safe. A parked thread doesn't need that wakeup to leave. A spurious wakeup or a preemption after the store is enough for the task to go away. So if the coredump client is preempted between the store and wake_up_process() the thread can exit and be freed in the meantime and try_to_wake_up() takes pi_lock in freed memory. Hold rcu across the loop. Fixes: a94e2d408eae ("coredump: kill mm->core_done") Cc: stable@vger.kernel.org Acked-by: Oleg Nesterov Link: https://patch.msgid.link/20260921-work-coredump-fixes-v3-1-8e4adb1619e6@kernel.org Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- fs/coredump.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/coredump.c +++ b/fs/coredump.c @@ -474,6 +474,8 @@ static void coredump_finish(bool core_du current->signal->core_state = NULL; spin_unlock_irq(¤t->sighand->siglock); + /* A released thread may exit and be freed before it is woken. */ + guard(rcu)(); while ((curr = next) != NULL) { next = curr->next; task = curr->task; @@ -482,6 +484,7 @@ static void coredump_finish(bool core_du * ->task == NULL before we read ->next. */ smp_mb(); + /* Any wakeup now lets the thread exit, rcu keeps it alive. */ curr->task = NULL; wake_up_process(task); }