thunderbolt: Fix NULL pointer dereference in tb_port_update_credits()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: thunderbolt: Fix NULL pointer dereference in tb_port_update_credits() Olliver reported that his system crashes when plugging in Thunderbolt 1 device: BUG: kernel NULL pointer dereference, address: 0000000000000020 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI RIP: 0010:tb_port_do_update_credits+0x1b/0x130 [thunderbolt] Call Trace: <TASK> ? __die+0x23/0x70 ? page_fault_oops+0x171/0x4e0 ? exc_page_fault+0x7f/0x180 ? asm_exc_page_fault+0x26/0x30 ? tb_port_do_update_credits+0x1b/0x130 ? tb_switch_update_link_attributes+0x83/0xd0 tb_switch_add+0x7a2/0xfe0 tb_scan_port+0x236/0x6f0 tb_handle_hotplug+0x6db/0x900 process_one_work+0x171/0x340 worker_thread+0x27b/0x3a0 ? __pfx_worker_thread+0x10/0x10 kthread+0xe5/0x120 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x31/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 </TASK> This is due the fact that some Thunderbolt 1 devices only have one lane adapter. Fix this by checking for the lane 1 before we read its credits.

References

• https://git.kernel.org/stable/c/440fba897c5ae32d7df1f1d609dbb19e2bba7fbb
• https://git.kernel.org/stable/c/ce64ba1f6ec3439e4b4d880b4db99673f4507228
• https://git.kernel.org/stable/c/d3d17e23d1a0d1f959b4fa55b35f1802d9c584fa