* [PATCH AUTOSEL 5.13 05/19] rcu-tasks: Don't delete holdouts within trc_inspect_reader()
[not found] <20210723035721.531372-1-sashal@kernel.org>
@ 2021-07-23 3:57 ` Sasha Levin
2021-07-23 3:57 ` [PATCH AUTOSEL 5.13 06/19] rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader() Sasha Levin
1 sibling, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2021-07-23 3:57 UTC (permalink / raw)
To: linux-kernel, stable; +Cc: Paul E. McKenney, Xu, Yanfei, Sasha Levin, rcu
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 350ebf5051f9..71e9d625371a 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -908,10 +908,9 @@ 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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH AUTOSEL 5.13 06/19] rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader()
[not found] <20210723035721.531372-1-sashal@kernel.org>
2021-07-23 3:57 ` [PATCH AUTOSEL 5.13 05/19] rcu-tasks: Don't delete holdouts within trc_inspect_reader() Sasha Levin
@ 2021-07-23 3:57 ` Sasha Levin
1 sibling, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2021-07-23 3:57 UTC (permalink / raw)
To: linux-kernel, stable; +Cc: Paul E. McKenney, Xu, Yanfei, Sasha Levin, rcu
From: "Paul E. McKenney" <paulmck@kernel.org>
[ Upstream commit a9ab9cce9367a2cc02a3c7eb57a004dc0b8f380d ]
Invoking trc_del_holdout() from within trc_wait_for_one_reader() is
only a performance optimization because the RCU Tasks Trace grace-period
kthread will eventually do this within check_all_holdout_tasks_trace().
But it is not a particularly important performance optimization because
it only applies to the grace-period kthread, of which there is but one.
This commit therefore removes this invocation of trc_del_holdout() in
favor of the one in check_all_holdout_tasks_trace() in the grace-period
kthread.
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 | 1 -
1 file changed, 1 deletion(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 71e9d625371a..fcef5f0c60b8 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -937,7 +937,6 @@ static void trc_wait_for_one_reader(struct task_struct *t,
// The current task had better be in a quiescent state.
if (t == current) {
t->trc_reader_checked = true;
- trc_del_holdout(t);
WARN_ON_ONCE(t->trc_reader_nesting);
return;
}
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
end of thread, other threads:[~2021-07-23 3:57 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <20210723035721.531372-1-sashal@kernel.org>
2021-07-23 3:57 ` [PATCH AUTOSEL 5.13 05/19] rcu-tasks: Don't delete holdouts within trc_inspect_reader() Sasha Levin
2021-07-23 3:57 ` [PATCH AUTOSEL 5.13 06/19] rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader() Sasha Levin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).