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    Subject[PATCH AUTOSEL 5.4 01/17] af_key: relax availability checks for skb size calculation
    Date
    From: Cong Wang <cong.wang@bytedance.com>

    [ 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>
    ---
    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 a915bc86620af..907d04a474597 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);
    }
    }
    --
    2.27.0
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