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From 2ea52a2fb8e87067e26bbab4efb8872639240eb0 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 21 Sep 2023 08:46:26 +0000
Subject: net: fix possible store tearing in neigh_periodic_work()
[ Upstream commit 25563b581ba3a1f263a00e8c9a97f5e7363be6fd ]
While looking at a related syzbot report involving neigh_periodic_work(),
I found that I forgot to add an annotation when deleting an
RCU protected item from a list.
Readers use rcu_deference(*np), we need to use either
rcu_assign_pointer() or WRITE_ONCE() on writer side
to prevent store tearing.
I use rcu_assign_pointer() to have lockdep support,
this was the choice made in neigh_flush_dev().
Fixes: 767e97e1e0db ("neigh: RCU conversion of struct neighbour")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/neighbour.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 3b642c412cf322..15267428c4f83d 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -935,7 +935,9 @@ static void neigh_periodic_work(struct work_struct *work)
if (refcount_read(&n->refcnt) == 1 &&
(state == NUD_FAILED ||
time_after(jiffies, n->used + NEIGH_VAR(n->parms, GC_STALETIME)))) {
- *np = n->next;
+ rcu_assign_pointer(*np,
+ rcu_dereference_protected(n->next,
+ lockdep_is_held(&tbl->lock)));
neigh_mark_dead(n);
write_unlock(&n->lock);
neigh_cleanup_and_release(n);
--
cgit 1.2.3-korg
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