From nobody Wed Apr 15 16:26:47 2026 Received: from mail115-24.sinamail.sina.com.cn (mail115-24.sinamail.sina.com.cn [218.30.115.24]) (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 47C6330DD16 for ; Wed, 4 Mar 2026 02:57:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=218.30.115.24 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772593052; cv=none; b=dbMC8slqvHuRMSL3qpDgkCx18WJDNNxzz5lS59SjGodEgjEK6yh+H45a3Ysc7Ew+NSHw2lD1aKqBCVxcPYvi2KWqerNMkM9lUJiZVnhe7dhdhBfaM41mh5iBlSIAHnJhlNdjAi1GB8ryZEUwesl4dtfn7yMuni/35KLqobwsZuY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772593052; c=relaxed/simple; bh=qkeRbo78B+2gM+r2nbeXSUfeM0u2W8lSayzGSDjRBRc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=FCnNfrKdBxbJT1jfBWDHw4VhDx3uOpUmljDr3tZI/Z+ZAsIjbfVWuP1DRO5yH8na07NxEDE0iA7aSmelRtBwGsjPjGWikq3mPE0s6kGr1krl5WCnEm1VQ/6kaa/Yq1qRipzSg6ETD5LCKLUnxm0xSVJR1HnoM7cV2ndegVMkk9I= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.cn; spf=pass smtp.mailfrom=sina.cn; dkim=pass (1024-bit key) header.d=sina.cn header.i=@sina.cn header.b=Wh2MP7Fu; arc=none smtp.client-ip=218.30.115.24 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.cn Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=sina.cn header.i=@sina.cn header.b="Wh2MP7Fu" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.cn; s=201208; t=1772593049; bh=DCsWQhNqFPEinGuq6D8087JmXqNHHQaNhOmiVDfpepM=; h=From:Subject:Date:Message-Id; b=Wh2MP7FuVtwFGixupGwVwA24K0+RckFi3fPlIya9nqsUY3ppc+gBaU+yitdC2Lhda PjwwEOm78x4xox73A4PRssuwmI+VHqvJf7c4m7m1MrUweDefX+5A2Of5uX3+5FI04r Y+usc50onLmq/QSkDu0SeVCr6VI8yfC3bnmvFmx8= X-SMAIL-HELO: NTT-kernel-dev Received: from unknown (HELO NTT-kernel-dev)([60.247.85.88]) by sina.cn (10.185.250.22) with ESMTP id 69A79F9400002FF7; Wed, 4 Mar 2026 10:57:26 +0800 (CST) X-Sender: jianqkang@sina.cn X-Auth-ID: jianqkang@sina.cn Authentication-Results: sina.cn; spf=none smtp.mailfrom=jianqkang@sina.cn; dkim=none header.i=none; dmarc=none action=none header.from=jianqkang@sina.cn X-SMAIL-MID: 7820897602635 X-SMAIL-UIID: 7B04746125BA4BD6BB653162830FBA2D-20260304-105726-1 From: Jianqiang kang To: gregkh@linuxfoundation.org, stable@vger.kernel.org, qiang.zhang1211@gmail.com Cc: patches@lists.linux.dev, linux-kernel@vger.kernel.org, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, rcu@vger.kernel.org, neeraj.upadhyay@kernel.org Subject: [PATCH 6.6.y] rcu/nocb: Fix possible invalid rdp's->nocb_cb_kthread pointer access Date: Wed, 4 Mar 2026 10:57:24 +0800 Message-Id: <20260304025724.2365669-1-jianqkang@sina.cn> X-Mailer: git-send-email 2.34.1 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 [ Upstream commit 1bba3900ca18bdae28d1b9fa10f16a8f8cb2ada1 ] 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) [ Minor conflict resolved. ] Signed-off-by: Jianqiang kang --- 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 8993b2322be2..a3d613f063a8 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1221,7 +1221,6 @@ static long rcu_nocb_rdp_offload(void *arg) struct rcu_segcblist *cblist =3D &rdp->cblist; unsigned long flags; int wake_gp; - struct rcu_data *rdp_gp =3D rdp->nocb_gp_rdp; =20 WARN_ON_ONCE(rdp->cpu !=3D raw_smp_processor_id()); /* @@ -1231,7 +1230,7 @@ static long rcu_nocb_rdp_offload(void *arg) 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); @@ -1260,7 +1259,7 @@ static long rcu_nocb_rdp_offload(void *arg) */ wake_gp =3D rdp_offload_toggle(rdp, true, flags); if (wake_gp) - wake_up_process(rdp_gp->nocb_gp_kthread); + wake_up_process(rdp->nocb_gp_kthread); swait_event_exclusive(rdp->nocb_state_wq, rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB) && rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)); --=20 2.34.1