From 81bc258370c6eeb1f41d350325e8a2c8e20fafad Mon Sep 17 00:00:00 2001 From: Mark Tomlinson Date: Mon, 8 Mar 2021 14:24:13 +1300 Subject: netfilter: x_tables: Use correct memory barriers. [ Upstream commit 175e476b8cdf2a4de7432583b49c871345e4f8a1 ] When a new table value was assigned, it was followed by a write memory barrier. This ensured that all writes before this point would complete before any writes after this point. However, to determine whether the rules are unused, the sequence counter is read. To ensure that all writes have been done before these reads, a full memory barrier is needed, not just a write memory barrier. The same argument applies when incrementing the counter, before the rules are read. Changing to using smp_mb() instead of smp_wmb() fixes the kernel panic reported in cc00bcaa5899 (which is still present), while still maintaining the same speed of replacing tables. The smb_mb() barriers potentially slow the packet path, however testing has shown no measurable change in performance on a 4-core MIPS64 platform. Fixes: 7f5c6d4f665b ("netfilter: get rid of atomic ops in fast path") Signed-off-by: Mark Tomlinson Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin --- net/netfilter/x_tables.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net') diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index 8b83806f4f8c..c9fe35118b33 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -1394,7 +1394,7 @@ xt_replace_table(struct xt_table *table, table->private = newinfo; /* make sure all cpus see new ->private value */ - smp_wmb(); + smp_mb(); /* * Even though table entries have now been swapped, other CPU's -- cgit v1.2.3