CVE-2022-48997 — char: tpm: Protect tpm_pm_suspend with locks

Affected: Linux

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]

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CVE-2022-48997 — char: tpm: Protect tpm_pm_suspend with locks