Messages in this thread Patch in this message | | | Date | Tue, 12 Apr 2011 07:35:09 -0700 | From | Greg KH <> | Subject | [080/105] netfilter: xtables: fix reentrancy |
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2.6.38-stable review patch. If anyone has any objections, please let us know.
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From: Eric Dumazet <eric.dumazet@gmail.com>
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>
--- net/ipv4/netfilter/ip_tables.c | 4 ++-- net/ipv6/netfilter/ip6_tables.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-)
--- 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 --- 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;
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