CVE-2022-48997

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

char: tpm: Protect tpmpmsuspend with locks

Currently tpm transactions are executed unconditionally in tpmpmsuspend() function, which may lead to races with other tpm accessors in the system.

Specifically, the hwrandom tpm driver makes use of tpmget_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: tpmtransmit: tpmrecv: error -52 tpm tpm0: invalid TPMSTS.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 1.16.0-20220807005459-localhost 04/01/2014 Call Trace: tpmtisstatus.cold+0x19/0x20 tpmtransmit+0x13b/0x390 tpmtransmitcmd+0x20/0x80 tpm1pmsuspend+0xa6/0x110 tpmpm_suspend+0x53/0x80 __pnpbussuspend+0x35/0xe0 _devicesuspend+0x10f/0x350

Fix this by calling tpmtrygetops(), which itself is a wrapper around tpmchip_start(), but takes the appropriate mutex.

[Jason: reworked commit message, added metadata]