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netfilter: conntrack: Avoid nf_ct_helper_hash uses after free

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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@vger.kernel.org
Fixes: 12f7a50533 ("netfilter: add user-space connection tracking helper infrastructure")
Signed-off-by: Florent Revest <revest@chromium.org>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Florent Revest 2023-07-03 16:52:16 +02:00 committed by Greg Kroah-Hartman
parent be6478f5cc
commit 8289d422f5
1 changed files with 4 additions and 0 deletions
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4
net/netfilter/nf_conntrack_helper.c
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@ -404,6 +404,9 @@ int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES); BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1); 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) if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
return -EINVAL; return -EINVAL;
@ -587,4 +590,5 @@ void nf_conntrack_helper_fini(void)
{ {
nf_ct_extend_unregister(&helper_extend); nf_ct_extend_unregister(&helper_extend);
kvfree(nf_ct_helper_hash); kvfree(nf_ct_helper_hash);
nf_ct_helper_hash = NULL;
} }