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Date: Sat, 26 Dec 2020 16:50:20 -0800 From: Cong Wang <xiyou.wangcong@...il.com> To: netdev@...r.kernel.org Cc: Cong Wang <cong.wang@...edance.com>, syzbot+b2bf2652983d23734c5c@...kaller.appspotmail.com, Steffen Klassert <steffen.klassert@...unet.com>, Herbert Xu <herbert@...dor.apana.org.au> Subject: [Patch net] af_key: relax availability checks for skb size calculation From: Cong Wang <cong.wang@...edance.com> 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@...kaller.appspotmail.com Cc: Steffen Klassert <steffen.klassert@...unet.com> Cc: Herbert Xu <herbert@...dor.apana.org.au> Signed-off-by: Cong Wang <cong.wang@...edance.com> --- 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 c12dbc51ef5f..ef9b4ac03e7b 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); } } -- 2.25.1
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