| Message ID | 20230703145216.1096265-1-revest@chromium.org |
|---|---|
| State | Accepted |
| Delegated to: | Pablo Neira |
| Headers | show |
| Series | [nf,v2] netfilter: conntrack: Avoid nf_ct_helper_hash uses after free | expand |
Florent Revest <revest@chromium.org> wrote: > 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. Reviewed-by: Florian Westphal <fw@strlen.de>
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; }
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@vger.kernel.org Fixes: 12f7a505331e ("netfilter: add user-space connection tracking helper infrastructure") Signed-off-by: Florent Revest <revest@chromium.org> --- net/netfilter/nf_conntrack_helper.c | 4 ++++ 1 file changed, 4 insertions(+)