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=1793207111; b=BjTCz0Rx6rO3r6FeZAM7udPq/SdmHsjoKEC0telTXt/53xj866tfqpdPwEHku4yzaRJK 7YDy+xjNUiXI9O1hNrRTIUEryrGj/NnnYRO2ywq86xCIkUxXJpZcoFvknWKA9czggrW5E Y3wEk/AHy+wOjY28SVHwM1FMhi1mpRCJ0NiO71TaPuxlE1+7UPUdylqwFWtMJwdJLPQl9 3CM9YS7RtlY8PfeWevVVtU2lfXHiEkxqZMEE4ifuCMzoW9fGvD48WC5Sxm9zSXL3oFQ+0 KMpaOGBHfidYCPpFAqnR7oYfgJAj6DACeAIidi9G1/3k5oqh8wINl4aDGFjbwjQZkdw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793207111; 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=c9zgXtS8QcvW5eoDvATXt4I/ImLGBwve1jIkR9G+uDg=; b=1JG8WaFofKWQ0UN3o/nOxswAv62wu6xyrf6EnZyvlZxK6T1H0JNAhCvU9810bmmQcGKq 2Dys6P1BQyH5xKnQ/ac6wQN8768g1FR/FKk2vlkcvitu5IF8CYeTgvrNVdgLCM1G3ngsP fxQ/nLQ0jDO6R2unppyqSF1WBIBXhmCaY+WIcW6qy84UAQknZdQbJKsnBtv9fw07iNYoh UIjmth8NctALrEWynDJy6+GXCk3738aI7lEsGnxVLbe3iXS+xxzmS+LwxBBNJAfRdgWKU iocdKK4Zk8BO9QJRvqJMfafUzKTbf1MCsYuLcBGlSPeDQBMHQT26UdKP6Wnv/LBX+NQ== 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=Mhe3PIzb; 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 899F7606A31A; Wed, 28 Oct 2026 17:05:11 +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=Mhe3PIzb Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D0B81F01828; Wed, 28 Oct 2026 17:05:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793207111; bh=c9zgXtS8QcvW5eoDvATXt4I/ImLGBwve1jIkR9G+uDg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Mhe3PIzbXkYfZZ+YqldLuRLqYMX5WwtKzzyQ88nwrsrX5HnUQl47dkVmV4khHYYLn ixID8vy2S90GUs02c9QnkNp9nlDkrazCjNCpYGLpDMxUAoerqUBtx7qWI6zlIvSZTI LtZiskTpZ36fjtSubFGJOILw4KXok2tFMwTKnXsw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Oleg Nesterov , "Christian Brauner (Amutable)" Subject: [PATCH 7.3 29/38] coredump: hold RCU while releasing parked threads Date: Wed, 28 Oct 2026 18:00:16 +0100 Message-ID: <20261028165941.144101001@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165940.394092994@linuxfoundation.org> References: <20261028165940.394092994@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 7.3-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 @@ -562,6 +562,8 @@ 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; @@ -570,6 +572,7 @@ 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); }