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In the Linux kernel, the following vulnerability has been resolved: usb: typec: tcpm: Check for port partner validity before consuming it typec_register_partner() does not guarantee partner registration to always succeed. In the event of failure, port->partner is set to the error value or NULL. Given that port->partner validity is not checked, this results in the following crash: Unable to handle kernel NULL pointer dereference at virtual address xx pc : run_state_machine+0x1bc8/0x1c08 lr : run_state_machine+0x1b90/0x1c08 .. Call trace: run_state_machine+0x1bc8/0x1c08 tcpm_state_machine_work+0x94/0xe4 kthread_worker_fn+0x118/0x328 kthread+0x1d0/0x23c ret_from_fork+0x10/0x20 To prevent the crash, check for port->partner validity before derefencing it in all the call sites.
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:
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}
}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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