From: Florent Revest <revest@xxxxxxxxxxxx>
commit 6eef7a2b933885a17679eb8ed0796ddf0ee5309b upstream.
If nf_conntrack_init_start() fails (for example due to a
register_nf_conntrack_bpf() failure), the nf_conntrack_helper_fini()
clean-up path frees the nf_ct_helper_hash map.
When built with NF_CONNTRACK=y, further netfilter modules (e.g:
netfilter_conntrack_ftp) can still be loaded and call
nf_conntrack_helpers_register(), independently of whether nf_conntrack
initialized correctly. This accesses the nf_ct_helper_hash dangling
pointer and causes a uaf, possibly leading to random memory corruption.
This patch guards nf_conntrack_helper_register() from accessing a freed
or uninitialized nf_ct_helper_hash pointer and fixes possible
uses-after-free when loading a conntrack module.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 12f7a505331e ("netfilter: add user-space connection tracking helper infrastructure")
Signed-off-by: Florent Revest <revest@xxxxxxxxxxxx>
Reviewed-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/netfilter/nf_conntrack_helper.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -404,6 +404,9 @@ int nf_conntrack_helper_register(struct
BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
+ if (!nf_ct_helper_hash)
+ return -ENOENT;
+
if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
return -EINVAL;
@@ -587,4 +590,5 @@ void nf_conntrack_helper_fini(void)
{
nf_ct_extend_unregister(&helper_extend);
kvfree(nf_ct_helper_hash);
+ nf_ct_helper_hash = NULL;
}
