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Subject[PATCH 5.2 114/137] 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 @@ access_check:
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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