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authorDennis Krein <Dennis.Krein@netapp.com>2018-10-26 07:38:24 -0700
committerPaul E. McKenney <paulmck@linux.ibm.com>2018-11-27 09:23:57 -0800
commiteb4c2382272ae7ae5d81fdfa5b7a6c86146eaaa4 (patch)
treee7ea6b85059f849898b1148ecf71228ea3a7b7a5
parent0607ba8403c4cdb253f8c5200ecf654dfb7790cc (diff)
srcu: Lock srcu_data structure in srcu_gp_start()
The srcu_gp_start() function is called with the srcu_struct structure's ->lock held, but not with the srcu_data structure's ->lock. This is problematic because this function accesses and updates the srcu_data structure's ->srcu_cblist, which is protected by that lock. Failing to hold this lock can result in corruption of the SRCU callback lists, which in turn can result in arbitrarily bad results. This commit therefore makes srcu_gp_start() acquire the srcu_data structure's ->lock across the calls to rcu_segcblist_advance() and rcu_segcblist_accelerate(), thus preventing this corruption. Reported-by: Bart Van Assche <bvanassche@acm.org> Reported-by: Christoph Hellwig <hch@infradead.org> Reported-by: Sebastian Kuzminsky <seb.kuzminsky@gmail.com> Signed-off-by: Dennis Krein <Dennis.Krein@netapp.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Dennis Krein <Dennis.Krein@netapp.com> Cc: <stable@vger.kernel.org> # 4.16.x
-rw-r--r--kernel/rcu/srcutree.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 60f3236beaf7..697a2d7e8e8a 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -451,10 +451,12 @@ static void srcu_gp_start(struct srcu_struct *sp)
lockdep_assert_held(&ACCESS_PRIVATE(sp, lock));
WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed));
+ spin_lock_rcu_node(sdp); /* Interrupts already disabled. */
rcu_segcblist_advance(&sdp->srcu_cblist,
rcu_seq_current(&sp->srcu_gp_seq));
(void)rcu_segcblist_accelerate(&sdp->srcu_cblist,
rcu_seq_snap(&sp->srcu_gp_seq));
+ spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */
smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */
rcu_seq_start(&sp->srcu_gp_seq);
state = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq));