* [PATCH 1/2] netfilter: xtables: fix reentrancy
@ 2011-03-18 17:05 Eric Dumazet
2011-03-20 14:40 ` Patrick McHardy
0 siblings, 1 reply; 2+ messages in thread
From: Eric Dumazet @ 2011-03-18 17:05 UTC (permalink / raw)
To: Patrick McHardy, David Miller
Cc: Netfilter Development Mailinglist, netdev, Jan Engelhardt
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>
Cc: Patrick McHardy <kaber@trash.net>
---
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 b09ed0d..ffcea0d 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 c9598a9..0b2af9b 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;
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 1/2] netfilter: xtables: fix reentrancy
2011-03-18 17:05 [PATCH 1/2] netfilter: xtables: fix reentrancy Eric Dumazet
@ 2011-03-20 14:40 ` Patrick McHardy
0 siblings, 0 replies; 2+ messages in thread
From: Patrick McHardy @ 2011-03-20 14:40 UTC (permalink / raw)
To: Eric Dumazet
Cc: David Miller, Netfilter Development Mailinglist, netdev, Jan Engelhardt
Am 18.03.2011 18:05, schrieb Eric Dumazet:
> 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.
Applied, thanks Eric.
^ permalink raw reply [flat|nested] 2+ messages in thread
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