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authorEric Dumazet <eric.dumazet@gmail.com>2011-03-20 15:40:06 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2011-04-14 13:02:31 -0700
commit53a080a724fd79d44132cc6e2f08246021503622 (patch)
tree127b2271529b60672548ec195aa9df9be458c885
parentebb12d3d3feb70061157ec5f71d7366f7b6e6dd9 (diff)
netfilter: xtables: fix reentrancy
commit db856674ac69e31946e56085239757cca3f7655f upstream. 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 <eric.dumazet@gmail.com> Cc: Jan Engelhardt <jengelh@medozas.de> Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--net/ipv4/netfilter/ip_tables.c4
-rw-r--r--net/ipv6/netfilter/ip6_tables.c4
2 files changed, 4 insertions, 4 deletions
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 3039101cbae..92fb4c5e5c9 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 7d227c644f7..830921e7e82 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;