rcu: Use *_ONCE() to protect lockless ->expmask accesses

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commit 15c7c972cd upstream.

The rcu_node structure's ->expmask field is accessed locklessly when
starting a new expedited grace period and when reporting an expedited
RCU CPU stall warning.  This commit therefore handles the former by
taking a snapshot of ->expmask while the lock is held and the latter
by applying READ_ONCE() to lockless reads and WRITE_ONCE() to the
corresponding updates.

Link: https://lore.kernel.org/lkml/CANpmjNNmSOagbTpffHr4=Yedckx9Rm2NuGqC9UqE+AOz5f1-ZQ@mail.gmail.com
Reported-by: syzbot+134336b86f728d6e55a0@syzkaller.appspotmail.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Paul E. McKenney 2019-10-07 18:53:18 -07:00 • committed by Greg Kroah-Hartman

parent 8771583c59

commit cf879a3489

1 changed files with 9 additions and 10 deletions

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kernel/rcu/tree_exp.h

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