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Subject[PATCH v3] char: tpm: Protect tpm_pm_suspend with locks
Date
From: Jan Dabros <jsd@semihalf.com>

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:

[ 3.277834] tpm tpm0: tpm_transmit: tpm_recv: error -52
[ 3.278437] tpm tpm0: invalid TPM_STS.x 0xff, dumping stack for forensics
[ 3.278445] CPU: 0 PID: 1 Comm: init Not tainted 6.1.0-rc5+ #135
[ 3.278450] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-20220807_005459-localhost 04/01/2014
[ 3.278453] Call Trace:
[ 3.278458] <TASK>
[ 3.278460] dump_stack_lvl+0x34/0x44
[ 3.278471] tpm_tis_status.cold+0x19/0x20
[ 3.278479] tpm_transmit+0x13b/0x390
[ 3.278489] tpm_transmit_cmd+0x20/0x80
[ 3.278496] tpm1_pm_suspend+0xa6/0x110
[ 3.278503] tpm_pm_suspend+0x53/0x80
[ 3.278510] __pnp_bus_suspend+0x35/0xe0
[ 3.278515] ? pnp_bus_freeze+0x10/0x10
[ 3.278519] __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.

Signed-off-by: Jan Dabros <jsd@semihalf.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Jason A. Donenfeld <Jason@zx2c4.com>
Tested-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/all/c5ba47ef-393f-1fba-30bd-1230d1b4b592@suse.cz/
Cc: stable@vger.kernel.org
Fixes: e891db1a18bf ("tpm: turn on TPM on suspend for TPM 1.x")
[Jason: reworked commit message, added metadata]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
drivers/char/tpm/tpm-interface.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 1621ce818705..d69905233aff 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -401,13 +401,14 @@ int tpm_pm_suspend(struct device *dev)
!pm_suspend_via_firmware())
goto suspended;

- if (!tpm_chip_start(chip)) {
+ rc = tpm_try_get_ops(chip);
+ if (!rc) {
if (chip->flags & TPM_CHIP_FLAG_TPM2)
tpm2_shutdown(chip, TPM2_SU_STATE);
else
rc = tpm1_pm_suspend(chip, tpm_suspend_pcr);

- tpm_chip_stop(chip);
+ tpm_put_ops(chip);
}

suspended:
--
2.38.1
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