af_key: relax availability checks for skb size calculation

BugLink: https://bugs.launchpad.net/bugs/1918158
[ Upstream commit afbc293add6466f8f3f0c3d944d85f53709c170f ]

xfrm_probe_algs() probes kernel crypto modules and changes the
availability of struct xfrm_algo_desc. But there is a small window
where ealg->available and aalg->available get changed between
count_ah_combs()/count_esp_combs() and dump_ah_combs()/dump_esp_combs(),
in this case we may allocate a smaller skb but later put a larger
amount of data and trigger the panic in skb_put().

Fix this by relaxing the checks when counting the size, that is,
skipping the test of ->available. We may waste some memory for a few
of sizeof(struct sadb_comb), but it is still much better than a panic.

Reported-by: syzbot+b2bf2652983d23734c5c@syzkaller.appspotmail.com
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/net/key/af_key.c b/net/key/af_key.c
index a915bc86620afe7a74c68ff684324a64e415c0d2..907d04a47459714690a2990443963240af698c4b 100644 (file)
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -2902,7 +2902,7 @@ static int count_ah_combs(const struct xfrm_tmpl *t)
                        break;
                if (!aalg->pfkey_supported)
                        continue;
-               if (aalg_tmpl_set(t, aalg) && aalg->available)
+               if (aalg_tmpl_set(t, aalg))
                        sz += sizeof(struct sadb_comb);
        }
        return sz + sizeof(struct sadb_prop);
@@ -2920,7 +2920,7 @@ static int count_esp_combs(const struct xfrm_tmpl *t)
                if (!ealg->pfkey_supported)
                        continue;
 
-               if (!(ealg_tmpl_set(t, ealg) && ealg->available))
+               if (!(ealg_tmpl_set(t, ealg)))
                        continue;
 
                for (k = 1; ; k++) {
@@ -2931,7 +2931,7 @@ static int count_esp_combs(const struct xfrm_tmpl *t)
                        if (!aalg->pfkey_supported)
                                continue;
 
-                       if (aalg_tmpl_set(t, aalg) && aalg->available)
+                       if (aalg_tmpl_set(t, aalg))
                                sz += sizeof(struct sadb_comb);
                }
        }