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security: smack: Fix possible null-pointer dereferences in smack_socket_sock_rcv_skb()

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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>
This commit is contained in:
Jia-Ju Bai 2019-07-23 18:00:15 +08:00 committed by Casey Schaufler
parent a1a07f2234
commit 3f4287e7d9
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1 changed files with 2 additions and 0 deletions
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security/smack/smack_lsm.c
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@ -3923,6 +3923,8 @@ access_check:
skp = smack_ipv6host_label(&sadd); skp = smack_ipv6host_label(&sadd);
if (skp == NULL) if (skp == NULL)
skp = smack_net_ambient; skp = smack_net_ambient;
if (skb == NULL)
break;
#ifdef CONFIG_AUDIT #ifdef CONFIG_AUDIT
smk_ad_init_net(&ad, __func__, LSM_AUDIT_DATA_NET, &net); smk_ad_init_net(&ad, __func__, LSM_AUDIT_DATA_NET, &net);
ad.a.u.net->family = family; ad.a.u.net->family = family;