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UPSTREAM: rcu-tasks: Don't delete holdouts within trc_inspect_reader()

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[ 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.

Bug: 202954022
Change-Id: Ib1e8eb51f74db89407462cadff1bc8c17565abb4
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>
This commit is contained in:
Paul E. McKenney
2021-05-25 10:12:45 -07:00
committed by Stephen Dickey
parent 2521995617
commit 354472cec0
1 changed files with 2 additions and 3 deletions
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5
kernel/rcu/tasks.h
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@@ -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!!!