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=1793209854; b=IU56+N27z7plL9kXAn9kZPxQN8cqdnE215xP3AM+0tZjzP4/bnAxz0pAAMzBwRtycNS2 cdXsndIBY/pVJSwRwbt6NQZlyrg5Izpd8//Tdmhm25fxCHXczQnIU11dKNMCLbqa+8FGp YWd6iMCl4R1grHlzfkxN9B6mvMRu80LZ6OrQTZqDjUScRWyQDmTJJjszSB58gCMFLqzCr OG2RGghp9j3cPzk9gG1pwNalPeEcSggLiPfeEMt7OJifxSHw6MWFCgN/eD22v+3ppyGIp wkH/BUnB/zw7M4H8cWJIpo1pSgGAHyT3OyvEAsP+7VQi/PzqktbYMXpedn9gzEWhCaw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793209854; 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=NP1U3QvIoWmFzfGP15MQWwoLdo+gpCbGjXVuovDFNYA=; b=0YTYCwRC8q7FI3xehpTV6p4HCMLlttngWAZGKK5ZCPzGjkRHYD0aPwLBOn6YAAFgnTr8 TEg6q4jLvTsMxz5fywT7wGLnLS23MzBdL7Ot2ilB9/VQAOJQTNkCzEEcbDgHyRoAOuaQD kgQQ7By2hHzDvVQ/7SO8jG0VA2No6j5n+vvGdI6hfJAXHue+viObu3iDWZboDvN9yz0WF MBZDCMLVegPUXuAArKw1QMacu/35cnvM+uBWYScaY7FJgEpBYyMUTH8GGxDICJX+NcQch ZrVbT5sKyudmOL4tKs/fubwhZ5aHHtThoD8JMb2FJo351kdlwGXzdTvC/+1uB2NOnTQ== 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=mPiLPc6Z; 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 08A28606A31D; Wed, 28 Oct 2026 17:50:54 +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=mPiLPc6Z Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A3B61F01825; Wed, 28 Oct 2026 17:50:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793209853; bh=NP1U3QvIoWmFzfGP15MQWwoLdo+gpCbGjXVuovDFNYA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mPiLPc6ZOE5PMOjhW3ORiY1KjPewZ2NCpZwKXYgzId3sm5vLvPCLkF9hWXQi2Ik9Y yNB72rv+pbEBo1Kg6I6VHlixCMsKVSFPtaHIhL11vErQwZD+U/1onEic0BwdxpBnXi Y4hDLUmM6Yg7xJ8aCOOonfE+3VmMc9ltAZzWpvu4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Oleg Nesterov , "Christian Brauner (Amutable)" Subject: [PATCH 6.18 101/109] coredump: hold RCU while releasing parked threads Date: Wed, 28 Oct 2026 18:01:25 +0100 Message-ID: <20261028165944.734031911@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165942.357251485@linuxfoundation.org> References: <20261028165942.357251485@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 6.18-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 @@ -560,6 +560,8 @@ 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; @@ -568,6 +570,7 @@ 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); }