UBUNTU-CVE-2021-46904

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UBUNTU-CVE-2021-46904

Summary:

Details: In the Linux kernel, the following vulnerability has been resolved: net: hso: fix null-ptr-deref during tty device unregistration Multiple ttys try to claim the same the minor number causing a double unregistration of the same device. The first unregistration succeeds but the next one results in a null-ptr-deref. The get_free_serial_index() function returns an available minor number but doesn't assign it immediately. The assignment is done by the caller later. But before this assignment, calls to get_free_serial_index() would return the same minor number. Fix this by modifying get_free_serial_index to assign the minor number immediately after one is found to be and rename it to obtain_minor() to better reflect what it does. Similary, rename set_serial_by_index() to release_minor() and modify it to free up the minor number of the given hso_serial. Every obtain_minor() should have corresponding release_minor() call.

References: https://ubuntu.com/security/CVE-2021-46904, https://git.kernel.org/linus/8a12f8836145ffe37e9c8733dce18c22fb668b66, https://www.cve.org/CVERecord?id=CVE-2021-46904, https://ubuntu.com/security/notices/USN-6971-1, https://ubuntu.com/security/notices/USN-6976-1