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From bdb062ede4003ee86bd6c2665b92856d69b14c6a Mon Sep 17 00:00:00 2001
From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Date: Wed, 10 Jun 2020 12:53:22 +0200
Subject: [PATCH 087/191] xfrm: Use sequence counter with associated spinlock
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.
Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.
If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.
Upstream-status: The xfrm locking used for seqcoun writer serialization
appears to be broken. If that's the case, a proper fix will need to be
submitted upstream. (e.g. make the seqcount per network namespace?)
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
net/xfrm/xfrm_state.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index d01ca1a18418..14059a9051b8 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -44,7 +44,7 @@ static void xfrm_state_gc_task(struct work_struct *work);
*/
static unsigned int xfrm_state_hashmax __read_mostly = 1 * 1024 * 1024;
-static __read_mostly seqcount_t xfrm_state_hash_generation = SEQCNT_ZERO(xfrm_state_hash_generation);
+static __read_mostly seqcount_spinlock_t xfrm_state_hash_generation;
static struct kmem_cache *xfrm_state_cache __ro_after_init;
static DECLARE_WORK(xfrm_state_gc_work, xfrm_state_gc_task);
@@ -139,6 +139,11 @@ static void xfrm_hash_resize(struct work_struct *work)
return;
}
+ /* XXX - the locking which protects the sequence counter appears
+ * to be broken here. The sequence counter is global, but the
+ * spinlock used for the sequence counter write serialization is
+ * per network namespace...
+ */
spin_lock_bh(&net->xfrm.xfrm_state_lock);
write_seqcount_begin(&xfrm_state_hash_generation);
@@ -2666,6 +2671,8 @@ int __net_init xfrm_state_init(struct net *net)
net->xfrm.state_num = 0;
INIT_WORK(&net->xfrm.state_hash_work, xfrm_hash_resize);
spin_lock_init(&net->xfrm.xfrm_state_lock);
+ seqcount_spinlock_init(&xfrm_state_hash_generation,
+ &net->xfrm.xfrm_state_lock);
return 0;
out_byspi:
--
2.19.1
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