Re: [PATCH v3] char: tpm: Protect tpm_pm_suspend with locks

From: Jason A. Donenfeld
Date: Sun Dec 04 2022 - 14:14:56 EST


On Sun, Dec 04, 2022 at 05:10:58PM +0000, Jarkko Sakkinen wrote:
> On Sun, Dec 04, 2022 at 05:06:41PM +0000, Jarkko Sakkinen wrote:
> > On Mon, Nov 28, 2022 at 08:56:51PM +0100, Jason A. Donenfeld wrote:
> > > From: Jan Dabros <jsd@xxxxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxxxx>
> > > Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
> > > Tested-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> > > Tested-by: Vlastimil Babka <vbabka@xxxxxxx>
> > > Link: https://lore.kernel.org/all/c5ba47ef-393f-1fba-30bd-1230d1b4b592@xxxxxxx/
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > 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@xxxxxxxxx>
> > > ---
> > > 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
> > >
> >
> > Hi, sorry for the latency.
> >
> > Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
>
> Applied to git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git

Oh thank goodness. You'll send this in for rc8 today?

Jason