diff options
| author | Florian Westphal <fw@strlen.de> | 2017-10-12 01:13:50 +0200 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2017-10-24 18:01:50 +0200 |
| commit | 80055dab5de0c8677bc148c4717ddfc753a9148e (patch) | |
| tree | 5d2be1a0944b420a9eb97af022424df0bed39b5f | |
| parent | eb6fad5a4a328b85d3faa8b301b522e3f316b49d (diff) | |
| download | blackbird-op-linux-80055dab5de0c8677bc148c4717ddfc753a9148e.tar.gz blackbird-op-linux-80055dab5de0c8677bc148c4717ddfc753a9148e.zip | |
netfilter: x_tables: make xt_replace_table wait until old rules are not used anymore
xt_replace_table relies on table replacement counter retrieval (which
uses xt_recseq to synchronize pcpu counters).
This is fine, however with large rule set get_counters() can take
a very long time -- it needs to synchronize all counters because
it has to assume concurrent modifications can occur.
Make xt_replace_table synchronize by itself by waiting until all cpus
had an even seqcount.
This allows a followup patch to copy the counters of the old ruleset
without any synchonization after xt_replace_table has completed.
Cc: Dan Williams <dcbw@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
| -rw-r--r-- | net/netfilter/x_tables.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index c83a3b5e1c6c..a164e5123d59 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -1153,6 +1153,7 @@ xt_replace_table(struct xt_table *table, int *error) { struct xt_table_info *private; + unsigned int cpu; int ret; ret = xt_jumpstack_alloc(newinfo); @@ -1182,14 +1183,28 @@ xt_replace_table(struct xt_table *table, smp_wmb(); table->private = newinfo; + /* make sure all cpus see new ->private value */ + smp_wmb(); + /* * Even though table entries have now been swapped, other CPU's - * may still be using the old entries. This is okay, because - * resynchronization happens because of the locking done - * during the get_counters() routine. + * may still be using the old entries... */ local_bh_enable(); + /* ... so wait for even xt_recseq on all cpus */ + for_each_possible_cpu(cpu) { + seqcount_t *s = &per_cpu(xt_recseq, cpu); + u32 seq = raw_read_seqcount(s); + + if (seq & 1) { + do { + cond_resched(); + cpu_relax(); + } while (seq == raw_read_seqcount(s)); + } + } + #ifdef CONFIG_AUDIT if (audit_enabled) { audit_log(current->audit_context, GFP_KERNEL, |
