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af_key: relax availability checks for skb size calculation

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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>
This commit is contained in:
Cong Wang 2020-12-26 16:50:20 -08:00 committed by Steffen Klassert
parent 9f8550e4bd
commit afbc293add
1 changed files with 3 additions and 3 deletions
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6
net/key/af_key.c
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@ -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);
}
}