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Fix module refcount dropping too far in 2.6.14

PATCH New Rusty Russell 1 participant 1 message Oct 31, 2005

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Rusty Russell

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PATCH 1/1 Fix module refcount dropping too far in 2.6.14

(Trivial, not compiled). The unknown protocol is used as a fallback when a protocol isn't known. Hence we cannot handle it failing, so don't set ".me". It's OK, since we only grab a reference from within the same module (iptable_nat.ko), so we never take the module refcount from 0 to 1.

Also, remove the "protocol is NULL" test: it's never NULL.

Signed-off-by Rusty Rusty <[email protected]>
net/ipv4/netfilter/ip_nat_core.c +2 -4
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.14/net/ipv4/netfilter/ip_nat_core.c working-2.6.14-proto-unknown-fix/net/ipv4/netfilter/ip_nat_core.c
@@ -66,10 +66,8 @@ ip_nat_proto_find_get(u_int8_t protonum)
 	 * removed until we've grabbed the reference */
 	preempt_disable();
 	p = __ip_nat_proto_find(protonum);
-	if (p) {
-		if (!try_module_get(p->me))
-			p = &ip_nat_unknown_protocol;
-	}
+	if (!try_module_get(p->me))
+		p = &ip_nat_unknown_protocol;
 	preempt_enable();
 
 	return p;
net/ipv4/netfilter/ip_nat_proto_unknown.c +1 -1
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.14/net/ipv4/netfilter/ip_nat_proto_unknown.c working-2.6.14-proto-unknown-fix/net/ipv4/netfilter/ip_nat_proto_unknown.c
@@ -62,7 +62,7 @@ unknown_print_range(char *buffer, const 
 
 struct ip_nat_protocol ip_nat_unknown_protocol = {
 	.name			= "unknown",
-	.me			= THIS_MODULE,
+	/* .me isn't set: getting a ref to this cannot fail. */
 	.manip_pkt		= unknown_manip_pkt,
 	.in_range		= unknown_in_range,
 	.unique_tuple		= unknown_unique_tuple,
Signature · 1 line
A bad analogy is like a leaky screwdriver -- Richard Braakman