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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-03-20 15:40:06 +0100 |
|---|---|---|
| committer | Patrick McHardy <kaber@trash.net> | 2011-03-20 15:40:06 +0100 |
| commit | db856674ac69e31946e56085239757cca3f7655f (patch) | |
| tree | 73fc82e92a119dcf1a0ce4e2ca45ef410165776f /net/ipv4 | |
| parent | 5c1aba467828bf0574ec5754c84884d573f590af (diff) | |
| download | lwn-db856674ac69e31946e56085239757cca3f7655f.tar.gz lwn-db856674ac69e31946e56085239757cca3f7655f.zip | |
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 <eric.dumazet@gmail.com>
Cc: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/netfilter/ip_tables.c | 4 |
1 files changed, 2 insertions, 2 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 |