From db856674ac69e31946e56085239757cca3f7655f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 20 Mar 2011 15:40:06 +0100 Subject: netfilter: xtables: fix reentrancy commit f3c5c1bfd4308 (make ip_tables reentrant) introduced a race in handling the stackptr restore, at the end of ipt_do_table() We should do it before the call to xt_info_rdunlock_bh(), or we allow cpu preemption and another cpu overwrites stackptr of original one. A second fix is to change the underflow test to check the origptr value instead of 0 to detect underflow, or else we allow a jump from different hooks. Signed-off-by: Eric Dumazet Cc: Jan Engelhardt Signed-off-by: Patrick McHardy --- net/ipv6/netfilter/ip6_tables.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/ipv6') diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index c9598a9067d7..0b2af9b85cec 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -410,7 +410,7 @@ ip6t_do_table(struct sk_buff *skb, verdict = (unsigned)(-v) - 1; break; } - if (*stackptr == 0) + if (*stackptr <= origptr) e = get_entry(table_base, private->underflow[hook]); else @@ -441,8 +441,8 @@ ip6t_do_table(struct sk_buff *skb, break; } while (!acpar.hotdrop); - xt_info_rdunlock_bh(); *stackptr = origptr; + xt_info_rdunlock_bh(); #ifdef DEBUG_ALLOW_ALL return NF_ACCEPT; -- cgit v1.2.2