tty: n_gsm: Don't block input queue by waiting MSC

Overview

In the Linux kernel, the following vulnerability has been resolved:

tty: n_gsm: Don't block input queue by waiting MSC

Currently gsm_queue() processes incoming frames and when opening a DLC channel it calls gsm_dlci_open() which calls gsm_modem_update(). If basic mode is used it calls gsm_modem_upd_via_msc() and it cannot block the input queue by waiting the response to come into the same input queue.

Instead allow sending Modem Status Command without waiting for remote end to respond. Define a new function gsm_modem_send_initial_msc() for this purpose. As MSC is only valid for basic encoding, it does not do anything for advanced or when convergence layer type 2 is used.

Affected

• Linux >= 48473802506d2d6151f59e0e764932b33b53cb3b < 8fcc22d6b90304d8b7436e101562218ea3faf73b
• Linux >= 48473802506d2d6151f59e0e764932b33b53cb3b < c36785f9de03df56ff9b8eca30fa681a12b2310d
• Linux >= 48473802506d2d6151f59e0e764932b33b53cb3b < 5416e89b81b00443cb03c88df8da097ae091a141
• Linux >= 48473802506d2d6151f59e0e764932b33b53cb3b < c5a2791a7f11939f05f95c01f0aec0c55bbf28d5
• Linux >= 48473802506d2d6151f59e0e764932b33b53cb3b < 3cf0b3c243e56bc43be560617416c1d9f301f44c
• Linux 920e849b7d23ced84c9d11e11e2449e34973cfb8
• Linux e83b4e1540469babeffcfd44a605cf8a61542598
• Linux >= 5.15.54 < 5.16
• Linux >= 5.17.6 < 5.18
• Linux 5.18

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.