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    Subject[PATCH AUTOSEL 5.2 28/42] security: smack: Fix possible null-pointer dereferences in smack_socket_sock_rcv_skb()
    Date
    From: Jia-Ju Bai <baijiaju1990@gmail.com>

    [ Upstream commit 3f4287e7d98a2954f20bf96c567fdffcd2b63eb9 ]

    In smack_socket_sock_rcv_skb(), there is an if statement
    on line 3920 to check whether skb is NULL:
    if (skb && skb->secmark != 0)

    This check indicates skb can be NULL in some cases.

    But on lines 3931 and 3932, skb is used:
    ad.a.u.net->netif = skb->skb_iif;
    ipv6_skb_to_auditdata(skb, &ad.a, NULL);

    Thus, possible null-pointer dereferences may occur when skb is NULL.

    To fix these possible bugs, an if statement is added to check skb.

    These bugs are found by a static analysis tool STCheck written by us.

    Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
    Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    security/smack/smack_lsm.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
    index 4c5e5a438f8bd..5c9fc8ba6e572 100644
    --- a/security/smack/smack_lsm.c
    +++ b/security/smack/smack_lsm.c
    @@ -3925,6 +3925,8 @@ static int smack_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
    skp = smack_ipv6host_label(&sadd);
    if (skp == NULL)
    skp = smack_net_ambient;
    + if (skb == NULL)
    + break;
    #ifdef CONFIG_AUDIT
    smk_ad_init_net(&ad, __func__, LSM_AUDIT_DATA_NET, &net);
    ad.a.u.net->family = family;
    --
    2.20.1
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