From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
"Xu, Yanfei" <yanfei.xu@windriver.com>,
Sasha Levin <sashal@kernel.org>,
rcu@vger.kernel.org
Subject: [PATCH AUTOSEL 5.10 05/17] rcu-tasks: Don't delete holdouts within trc_inspect_reader()
Date: Thu, 22 Jul 2021 23:57:36 -0400 [thread overview]
Message-ID: <20210723035748.531594-5-sashal@kernel.org> (raw)
In-Reply-To: <20210723035748.531594-1-sashal@kernel.org>
From: "Paul E. McKenney" <paulmck@kernel.org>
[ Upstream commit 1d10bf55d85d34eb73dd8263635f43fd72135d2d ]
As Yanfei pointed out, although invoking trc_del_holdout() is safe
from the viewpoint of the integrity of the holdout list itself,
the put_task_struct() invoked by trc_del_holdout() can result in
use-after-free errors due to later accesses to this task_struct structure
by the RCU Tasks Trace grace-period kthread.
This commit therefore removes this call to trc_del_holdout() from
trc_inspect_reader() in favor of the grace-period thread's existing call
to trc_del_holdout(), thus eliminating that particular class of
use-after-free errors.
Reported-by: "Xu, Yanfei" <yanfei.xu@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/rcu/tasks.h | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 73bbe792fe1e..208acb286ec2 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -879,10 +879,9 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
in_qs = likely(!t->trc_reader_nesting);
}
- // Mark as checked. Because this is called from the grace-period
- // kthread, also remove the task from the holdout list.
+ // Mark as checked so that the grace-period kthread will
+ // remove it from the holdout list.
t->trc_reader_checked = true;
- trc_del_holdout(t);
if (in_qs)
return true; // Already in quiescent state, done!!!
--
2.30.2
next parent reply other threads:[~2021-07-23 3:58 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210723035748.531594-1-sashal@kernel.org>
2021-07-23 3:57 ` Sasha Levin [this message]
2021-07-23 3:57 ` [PATCH AUTOSEL 5.10 06/17] rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader() Sasha Levin
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