If register_nf_conntrack_bpf() fails (for example, if the .BTF section
contains an invalid entry), nf_conntrack_init_start() calls
nf_conntrack_helper_fini() as part of its cleanup path and
nf_ct_helper_hash gets freed.
Further netfilter modules like netfilter_conntrack_ftp don't check
whether nf_conntrack initialized correctly and call
nf_conntrack_helpers_register() which accesses the freed
nf_ct_helper_hash and causes a uaf.
This patch guards nf_conntrack_helper_register() from accessing
freed/uninitialized nf_ct_helper_hash maps and fixes a boot-time
use-after-free.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 12f7a505331e ("netfilter: add user-space connection tracking helper infrastructure")
Signed-off-by: Florent Revest <revest@xxxxxxxxxxxx>
---
net/netfilter/nf_conntrack_helper.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 0c4db2f2ac43..f22691f83853 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -360,6 +360,9 @@ int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
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;
@@ -515,4 +518,5 @@ int nf_conntrack_helper_init(void)
void nf_conntrack_helper_fini(void)
{
kvfree(nf_ct_helper_hash);
+ nf_ct_helper_hash = NULL;
}
--
2.41.0.162.gfafddb0af9-goog
