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In the Linux kernel, the following vulnerability has been resolved: net: enetc: allocate vf_state during PF probes In the previous implementation, vf_state is allocated memory only when VF is enabled. However, net_device_ops::ndo_set_vf_mac() may be called before VF is enabled to configure the MAC address of VF. If this is the case, enetc_pf_set_vf_mac() will access vf_state, resulting in access to a null pointer. The simplified error log is as follows. root@ls1028ardb:~# ip link set eno0 vf 1 mac 00:0c:e7:66:77:89 [ 173.543315] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004 [ 173.637254] pc : enetc_pf_set_vf_mac+0x3c/0x80 Message from sy [ 173.641973] lr : do_setlink+0x4a8/0xec8 [ 173.732292] Call trace: [ 173.734740] enetc_pf_set_vf_mac+0x3c/0x80 [ 173.738847] __rtnl_newlink+0x530/0x89c [ 173.742692] rtnl_newlink+0x50/0x7c [ 173.746189] rtnetlink_rcv_msg+0x128/0x390 [ 173.750298] netlink_rcv_skb+0x60/0x130 [ 173.754145] rtnetlink_rcv+0x18/0x24 [ 173.757731] netlink_unicast+0x318/0x380 [ 173.761665] netlink_sendmsg+0x17c/0x3c8
CVSS 3.1 Base Score 5.5. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
While there are no complete fixes aside from conscientious programming, the following steps will go a long way to ensure that NULL pointer dereferences do not occur.
}
/* make use of pointer1 *//* ... */If you are working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the if statement; and unlock when it has finished.
This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.
}
strcpy(hostname, hp->h_name);/*routine that ensures user_supplied_addr is in the right format for conversion */If an attacker provides an address that appears to be well-formed, but the address does not resolve to a hostname, then the call to gethostbyaddr() will return NULL. Since the code does not check the return value from gethostbyaddr (CWE-252), a NULL pointer dereference would then occur in the call to strcpy().
Note that this example is also vulnerable to a buffer overflow (see CWE-119).
In the following code, the programmer assumes that the system always has a property named "cmd" defined. If an attacker can control the program's environment so that "cmd" is not defined, the program throws a NULL pointer exception when it attempts to call the trim() method.
cmd = cmd.trim();This application has registered to handle a URL when sent an intent:
}......
}
}int length = URL.length();...The application assumes the URL will always be included in the intent. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called.
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