From: Paul E. McKenney <paulmck@xxxxxxxxxx> [ 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@xxxxxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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
