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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-03-20 15:40:06 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-04-14 13:02:31 -0700 |
| commit | 53a080a724fd79d44132cc6e2f08246021503622 (patch) | |
| tree | 127b2271529b60672548ec195aa9df9be458c885 | |
| parent | ebb12d3d3feb70061157ec5f71d7366f7b6e6dd9 (diff) | |
| download | lwn-53a080a724fd79d44132cc6e2f08246021503622.tar.gz lwn-53a080a724fd79d44132cc6e2f08246021503622.zip | |
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.c | 4 | ||||
| -rw-r--r-- | 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 3039101cbaed..92fb4c5e5c9b 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 7d227c644f72..830921e7e82b 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; |