From 03d76df5f164a6bae2f10f0c9e29bc7da7e7c31e Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Sat, 26 Dec 2020 16:50:20 -0800 Subject: [PATCH] af_key: relax availability checks for skb size calculation [ 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 Cc: Herbert Xu Signed-off-by: Cong Wang Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- net/key/af_key.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/key/af_key.c b/net/key/af_key.c index a915bc86620a..907d04a47459 100644 --- 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); } }