Impact: fix log spam under CONFIG_DEBUG_PREEMPT=y This recent commit: 7845447: netfilter: iptables: lock free counters Converted a couple of netfilter codepaths from read_lock() critical sections to lockless rcu_read_lock(). What it forgot about is that under CONFIG_PREEMPT=y and CONFIG_PREEMPT_RCU=y these sections can be preempted. Under CONFIG_DEBUG_PREEMPT=y this produces such warnings: BUG: using smp_processor_id() in preemptible [00000000] code: ssh/9115 caller is ipt_do_table+0xc8/0x559 Pid: 9115, comm: ssh Tainted: G W 2.6.29-tip-08646-g45ef7c3-dirty #26231 Call Trace: [<c0c0dacf>] ? printk+0x14/0x16 [<c048c2e6>] debug_smp_processor_id+0xa6/0xbc [<c0adbd03>] ipt_do_table+0xc8/0x559 [<c0c10277>] ? _read_unlock+0x3d/0x49 [<c0ad68c0>] ? fn_hash_lookup+0x94/0xa0 [<c0ad330e>] ? __inet_dev_addr_type+0x56/0x8d [<c0a87b02>] ? neigh_lookup+0xe5/0x108 [<c0adc2bc>] ipt_local_hook+0x40/0x50 [<c0a93e57>] nf_iterate+0x34/0x80 [<c0aad4b8>] ? dst_output+0x0/0x10 [<c0a93eea>] nf_hook_slow+0x47/0xa4 [<c0aad4b8>] ? dst_output+0x0/0x10 [<c0aaec04>] __ip_local_out+0x78/0x7f [<c0aad4b8>] ? dst_output+0x0/0x10 [<c0aaec1b>] ip_local_out+0x10/0x20 [<c0aaf416>] ip_queue_xmit+0x2bc/0x332 [<c0aa8fdf>] ? __ip_route_output_key+0x112/0x77b [<c01397fe>] ? local_bh_enable+0x10/0x12 [<c0abf0e5>] ? tcp_connect+0x32a/0x3bb [<c0ab15a7>] ? __inet_hash_nolisten+0x97/0xaf [<c0a78dde>] ? __copy_skb_header+0xe/0x13a [<c0abf0e5>] ? tcp_connect+0x32a/0x3bb [<c0abe955>] ? tcp_transmit_skb+0x5a5/0x61c [<c0abe995>] tcp_transmit_skb+0x5e5/0x61c [<c0a7b6c0>] ? __alloc_skb+0x54/0x120 [<c0abefca>] ? tcp_connect+0x20f/0x3bb [<c0abf0e5>] tcp_connect+0x32a/0x3bb [<c0ac4b68>] tcp_v4_connect+0x466/0x4be [<c0acf380>] inet_stream_connect+0x8f/0x212 [<c018f4e6>] ? might_fault+0x75/0x77 [<c047f198>] ? copy_from_user+0x2f/0x117 BUG: using smp_processor_id() in preemptible [00000000] code: ssh/9114 Since it appears that the tables are RCU freed, and there are no non-preempt assumptions in the code, the using of raw_smp_processor_id() is safe. [ I also audited all of net/netfilter/*.c for smp_processor_id() use, and fixed all places that used them unsafely. ] Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- net/ipv4/netfilter/arp_tables.c | 2 +- net/ipv4/netfilter/ip_tables.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index 35c5f6a..30baf3e 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -255,7 +255,7 @@ unsigned int arpt_do_table(struct sk_buff *skb, rcu_read_lock(); private = rcu_dereference(table->private); - table_base = rcu_dereference(private->entries[smp_processor_id()]); + table_base = rcu_dereference(private->entries[raw_smp_processor_id()]); e = get_entry(table_base, private->hook_entry[hook]); back = get_entry(table_base, private->underflow[hook]); diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 82ee7c9..eff124e 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -280,7 +280,7 @@ static void trace_packet(struct sk_buff *skb, char *hookname, *chainname, *comment; unsigned int rulenum = 0; - table_base = (void *)private->entries[smp_processor_id()]; + table_base = (void *)private->entries[raw_smp_processor_id()]; root = get_entry(table_base, private->hook_entry[hook]); hookname = chainname = (char *)hooknames[hook]; @@ -341,7 +341,7 @@ ipt_do_table(struct sk_buff *skb, rcu_read_lock(); private = rcu_dereference(table->private); - table_base = rcu_dereference(private->entries[smp_processor_id()]); + table_base = rcu_dereference(private->entries[raw_smp_processor_id()]); e = get_entry(table_base, private->hook_entry[hook]); -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
