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SubjectRe: An oops while running 2.5.65-mm2
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On Fri, 2003-03-21 at 02:19, Martin Josefsson wrote:

> You are correct. It was a list_del() that caused it (at least I think
> so, it's 2am right now).
>
> 1. conntrack helper adds an expectation and adds that to a list hanging
> of off a connection.
>
> 2. the expected connection arrives. the expectation is still on the
> list.
>
> 3. the original connection that caused the expectation terminates but
> the expectation still thinks it's added to the list.
>
> 4. the expected connection terminates and list_del() is called to remove
> it from the list which doesn't exist anymore. boom!

Ok, the previous patch was a little bit incorrect. It did fix the use
after free bug (which can cause corruption if the slabmemory is
reallocated before we write to it) but lost some internal information.
I can't see that we use this anywhere after this point but here's the
proper patch.

Sorry about that.


--- linux-2.5.64-bk10/net/ipv4/netfilter/ip_conntrack_core.c.orig 2003-03-21 01:42:57.000000000 +0100
+++ linux-2.5.64-bk10/net/ipv4/netfilter/ip_conntrack_core.c 2003-03-22 00:43:28.000000000 +0100
@@ -274,6 +274,7 @@
* the un-established ones only */
if (exp->sibling) {
DEBUGP("remove_expectations: skipping established %p of %p\n", exp->sibling, ct);
+ exp->expectant = NULL;
continue;
}

@@ -327,9 +328,11 @@
WRITE_LOCK(&ip_conntrack_lock);
/* Delete our master expectation */
if (ct->master) {
- /* can't call __unexpect_related here,
- * since it would screw up expect_list */
- list_del(&ct->master->expected_list);
+ if (ct->master->expectant) {
+ /* can't call __unexpect_related here,
+ * since it would screw up expect_list */
+ list_del(&ct->master->expected_list);
+ }
kfree(ct->master);
}
WRITE_UNLOCK(&ip_conntrack_lock);
--
/Martin
Never argue with an idiot. They drag you down to their level, then beat you with experience.
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