From nobody Tue Oct 7 15:01:30 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 357E72C08D1; Wed, 9 Jul 2025 10:47:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752058026; cv=none; b=XHCKwpG5vg+DopM5659rnyWfV9liuWsvmc8UevWqtHSVYmZb1I5HMBiDFn/9XoBoD4d/9y8w16g+Y0gFt/uwqHz+JtJN/LArrie7m8e+6wfwlUyL58h6HA/JS9o/JaDLy05aqg8CKkxkwJ7nhg+VRuvNb+k9TXoaanCbPuJVeQQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752058026; c=relaxed/simple; bh=e1BHcaYIkCpx/CHPZ4PtOBHjn/DmOqQFeLNeR8CAhZY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=tbnyTKVxx/fjqGPEMg6UcLHAI1XdyxISk7GtqlUEybeGsgqNsuQYTqd1ux8z2+5RMhFcBl5ykw2Rp5P/IRCn0KgInugJb8EZ+qVItig6xJLR7k+WMncSmDBzyuktQsou3k+mB0LJKfwKtjXafbpXUPgZf/YCUuX7U0yWo1g1Uic= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ekI3f6MO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ekI3f6MO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 995E5C4CEEF; Wed, 9 Jul 2025 10:47:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752058026; bh=e1BHcaYIkCpx/CHPZ4PtOBHjn/DmOqQFeLNeR8CAhZY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ekI3f6MOrT72oUwkHmg5gafW55hBKdRwTVZPxtUWaFkH6yrkXiwzXmovAjm7u4HxD Ij11IbyMPD+UFF6Ol/UFDt0aqZiOTXXpgrEItbpEyqqs1u4lzTo8C47KZ8vY9UOmpi d5O+FLpu/pg48gVX4eur9g2VDJZz3TwAhyCtV73dyBQO4rYSD1zL58USxijLGiUyuj N0v9FoCHxtTVgsSIo0g4s0W4ADjnNmpz6u5BYve6n64bx3W9gIJBiG5lTuwvoXbsGX vbawmB7Ey1mcvkKI+/HFg4M1EQ+CAURRayoGibU965MJ6PRjaC00AtvMQ2wgDDPwH8 d9IAMP77Phcbg== From: neeraj.upadhyay@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, paulmck@kernel.org, joelagnelf@nvidia.com, frederic@kernel.org, boqun.feng@gmail.com, urezki@gmail.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang1211@gmail.com, neeraj.iitr10@gmail.com, neeraj.upadhyay@amd.com, "Neeraj Upadhyay (AMD)" Subject: [PATCH rcu 2/2] rcu/nocb: Fix possible invalid rdp's->nocb_cb_kthread pointer access Date: Wed, 9 Jul 2025 16:16:41 +0530 Message-Id: <20250709104641.15699-3-neeraj.upadhyay@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20250709104641.15699-1-neeraj.upadhyay@kernel.org> References: <20250709104641.15699-1-neeraj.upadhyay@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Zqiang In the preparation stage of CPU online, if the corresponding the rdp's->nocb_cb_kthread does not exist, will be created, there is a situation where the rdp's rcuop kthreads creation fails, and then de-offload this CPU's rdp, does not assign this CPU's rdp->nocb_cb_kthread pointer, but this rdp's->nocb_gp_rdp and rdp's->rdp_gp->nocb_gp_kthread is still valid. This will cause the subsequent re-offload operation of this offline CPU, which will pass the conditional check and the kthread_unpark() will access invalid rdp's->nocb_cb_kthread pointer. This commit therefore use rdp's->nocb_gp_kthread instead of rdp_gp's->nocb_gp_kthread for safety check. Signed-off-by: Zqiang Reviewed-by: Frederic Weisbecker Signed-off-by: Neeraj Upadhyay (AMD) --- kernel/rcu/tree_nocb.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index cb29b6bb0ed4..08eb9b0e2fab 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1146,7 +1146,6 @@ static bool rcu_nocb_rdp_offload_wait_cond(struct rcu= _data *rdp) static int rcu_nocb_rdp_offload(struct rcu_data *rdp) { int wake_gp; - struct rcu_data *rdp_gp =3D rdp->nocb_gp_rdp; =20 WARN_ON_ONCE(cpu_online(rdp->cpu)); /* @@ -1156,7 +1155,7 @@ static int rcu_nocb_rdp_offload(struct rcu_data *rdp) if (!rdp->nocb_gp_rdp) return -EINVAL; =20 - if (WARN_ON_ONCE(!rdp_gp->nocb_gp_kthread)) + if (WARN_ON_ONCE(!rdp->nocb_gp_kthread)) return -EINVAL; =20 pr_info("Offloading %d\n", rdp->cpu); @@ -1166,7 +1165,7 @@ static int rcu_nocb_rdp_offload(struct rcu_data *rdp) =20 wake_gp =3D rcu_nocb_queue_toggle_rdp(rdp); if (wake_gp) - wake_up_process(rdp_gp->nocb_gp_kthread); + wake_up_process(rdp->nocb_gp_kthread); =20 swait_event_exclusive(rdp->nocb_state_wq, rcu_nocb_rdp_offload_wait_cond(rdp)); --=20 2.40.1