* Patch "rcu/nocb: Fix possible invalid rdp's->nocb_cb_kthread pointer access" has been added to the 6.1-stable tree
2026-03-04 2:49 [PATCH 6.1.y] rcu/nocb: Fix possible invalid rdp's->nocb_cb_kthread pointer access Jianqiang kang
@ 2026-03-23 13:03 ` gregkh
0 siblings, 0 replies; 2+ messages in thread
From: gregkh @ 2026-03-23 13:03 UTC (permalink / raw)
To: frederic, gregkh, jiangshanlai, jianqkang, joel, josh,
mathieu.desnoyers, neeraj.upadhyay, patches, paulmck,
qiang.zhang1211, quic_neeraju, rostedt
Cc: stable-commits
This is a note to let you know that I've just added the patch titled
rcu/nocb: Fix possible invalid rdp's->nocb_cb_kthread pointer access
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rcu-nocb-fix-possible-invalid-rdp-s-nocb_cb_kthread-pointer-access.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From jianqkang@sina.cn Wed Mar 4 03:49:40 2026
From: Jianqiang kang <jianqkang@sina.cn>
Date: Wed, 4 Mar 2026 10:49:34 +0800
Subject: rcu/nocb: Fix possible invalid rdp's->nocb_cb_kthread pointer access
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
Message-ID: <20260304024934.2364383-1-jianqkang@sina.cn>
From: Zqiang <qiang.zhang1211@gmail.com>
[ 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 <qiang.zhang1211@gmail.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
[ Minor conflict resolved. ]
Signed-off-by: Jianqiang kang <jianqkang@sina.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/rcu/tree_nocb.h | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1112,7 +1112,6 @@ static long rcu_nocb_rdp_offload(void *a
struct rcu_segcblist *cblist = &rdp->cblist;
unsigned long flags;
int wake_gp;
- struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id());
/*
@@ -1122,7 +1121,7 @@ static long rcu_nocb_rdp_offload(void *a
if (!rdp->nocb_gp_rdp)
return -EINVAL;
- if (WARN_ON_ONCE(!rdp_gp->nocb_gp_kthread))
+ if (WARN_ON_ONCE(!rdp->nocb_gp_kthread))
return -EINVAL;
pr_info("Offloading %d\n", rdp->cpu);
@@ -1151,7 +1150,7 @@ static long rcu_nocb_rdp_offload(void *a
*/
wake_gp = 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));
Patches currently in stable-queue which might be from jianqkang@sina.cn are
queue-6.1/riscv-stacktrace-disable-kasan-checks-for-non-current-tasks.patch
queue-6.1/rcu-nocb-fix-possible-invalid-rdp-s-nocb_cb_kthread-pointer-access.patch
queue-6.1/io_uring-io-wq-check-io_wq_bit_exit-inside-work-run-loop.patch
^ permalink raw reply [flat|nested] 2+ messages in thread