rcu-tasks: Don't delete holdouts within trc_inspect_reader()
authorPaul E. McKenney <paulmck@kernel.org>
Tue, 25 May 2021 17:12:45 +0000 (10:12 -0700)
committerPaul E. McKenney <paulmck@kernel.org>
Tue, 6 Jul 2021 19:38:21 +0000 (12:38 -0700)
commit1d10bf55d85d34eb73dd8263635f43fd72135d2d
tree098a4e33b5347ac9c22257dc313f2b5528c982e6
parent05bc276cf243d90b9f1eb6ae2962f41eeb53a741
rcu-tasks: Don't delete holdouts within trc_inspect_reader()

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>
kernel/rcu/tasks.h