char: tpm: Protect tpm_pm_suspend with locks

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

char: tpm: Protect tpm_pm_suspend with locks

Currently tpm transactions are executed unconditionally in

tpm_pm_suspend() function, which may lead to races with other tpm

accessors in the system.

Specifically, the hw_random tpm driver makes use of tpm_get_random(),

and this function is called in a loop from a kthread, which means it's

not frozen alongside userspace, and so can race with the work done

during system suspend:

tpm tpm0: tpm_transmit: tpm_recv: error -52

tpm tpm0: invalid TPM_STS.x 0xff, dumping stack for forensics

CPU: 0 PID: 1 Comm: init Not tainted 6.1.0-rc5+ #135

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-20220807_005459-localhost 04/01/2014

Call Trace:

tpm_tis_status.cold+0x19/0x20

tpm_transmit+0x13b/0x390

tpm_transmit_cmd+0x20/0x80

tpm1_pm_suspend+0xa6/0x110

tpm_pm_suspend+0x53/0x80

__pnp_bus_suspend+0x35/0xe0

__device_suspend+0x10f/0x350

Fix this by calling tpm_try_get_ops(), which itself is a wrapper around

tpm_chip_start(), but takes the appropriate mutex.

[Jason: reworked commit message, added metadata]