From db856674ac69e31946e56085239757cca3f7655f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 20 Mar 2011 15:40:06 +0100 Subject: [PATCH] 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/ipv4/netfilter/ip_tables.c | 4 ++-- net/ipv6/netfilter/ip6_tables.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index b09ed0d080f9..ffcea0d1678e 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -387,7 +387,7 @@ ipt_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]); pr_debug("Underflow (this is normal) " @@ -427,10 +427,10 @@ ipt_do_table(struct sk_buff *skb, /* Verdict */ break; } while (!acpar.hotdrop); - xt_info_rdunlock_bh(); pr_debug("Exiting %s; resetting sp from %u to %u\n", __func__, *stackptr, origptr); *stackptr = origptr; + xt_info_rdunlock_bh(); #ifdef DEBUG_ALLOW_ALL return NF_ACCEPT; #else 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;