On Fri Nov 1, 2024 at 11:09 PM EET, Jerry Snitselaar wrote: > On Fri, Nov 01, 2024 at 11:07:15PM +0200, Jarkko Sakkinen wrote: > > On Fri Nov 1, 2024 at 10:23 PM EET, Jerry Snitselaar wrote: > > > On Fri, Nov 01, 2024 at 02:21:56AM +0200, Jarkko Sakkinen wrote: > > > > Setting TPM_CHIP_FLAG_SUSPENDED in the end of tpm_pm_suspend() can be > > > > racy > > > > according, as this leaves window for tpm_hwrng_read() to be called while > > > > the operation is in progress. The recent bug report gives also evidence > > > > of > > > > this behaviour. > > > > > > > > Aadress this by locking the TPM chip before checking any chip->flags > > > > both > > > > in tpm_pm_suspend() and tpm_hwrng_read(). Move TPM_CHIP_FLAG_SUSPENDED > > > > check inside tpm_get_random() so that it will be always checked only > > > > when > > > > the lock is reserved. > > > > > > > > Cc: [email protected] # v6.4+ > > > > Fixes: 99d464506255 ("tpm: Prevent hwrng from activating during resume") > > > > Reported-by: Mike Seo <[email protected]> > > > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219383 > > > > Signed-off-by: Jarkko Sakkinen <[email protected]> > > > > --- > > > > v3: > > > > - Check TPM_CHIP_FLAG_SUSPENDED inside tpm_get_random() so that it is > > > > also done under the lock (suggested by Jerry Snitselaar). > > > > v2: > > > > - Addressed my own remark: > > > > > > > > https://lore.kernel.org/linux-integrity/[email protected]/ > > > > --- > > > > drivers/char/tpm/tpm-chip.c | 4 ---- > > > > drivers/char/tpm/tpm-interface.c | 32 ++++++++++++++++++++++---------- > > > > 2 files changed, 22 insertions(+), 14 deletions(-) > > > > > > > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c > > > > index 1ff99a7091bb..7df7abaf3e52 100644 > > > > --- a/drivers/char/tpm/tpm-chip.c > > > > +++ b/drivers/char/tpm/tpm-chip.c > > > > @@ -525,10 +525,6 @@ static int tpm_hwrng_read(struct hwrng *rng, void > > > > *data, size_t max, bool wait) > > > > { > > > > struct tpm_chip *chip = container_of(rng, struct tpm_chip, > > > > hwrng); > > > > > > > > - /* Give back zero bytes, as TPM chip has not yet fully resumed: > > > > */ > > > > - if (chip->flags & TPM_CHIP_FLAG_SUSPENDED) > > > > - return 0; > > > > - > > > > return tpm_get_random(chip, data, max); > > > > } > > > > > > > > diff --git a/drivers/char/tpm/tpm-interface.c > > > > b/drivers/char/tpm/tpm-interface.c > > > > index 8134f002b121..b1daa0d7b341 100644 > > > > --- a/drivers/char/tpm/tpm-interface.c > > > > +++ b/drivers/char/tpm/tpm-interface.c > > > > @@ -370,6 +370,13 @@ int tpm_pm_suspend(struct device *dev) > > > > if (!chip) > > > > return -ENODEV; > > > > > > > > + rc = tpm_try_get_ops(chip); > > > > + if (rc) { > > > > + /* Can be safely set out of locks, as no action cannot > > > > race: */ > > > > + chip->flags |= TPM_CHIP_FLAG_SUSPENDED; > > > > + goto out; > > > > + } > > > > + > > > > if (chip->flags & TPM_CHIP_FLAG_ALWAYS_POWERED) > > > > goto suspended; > > > > > > > > @@ -377,21 +384,19 @@ int tpm_pm_suspend(struct device *dev) > > > > !pm_suspend_via_firmware()) > > > > goto suspended; > > > > > > > > - rc = tpm_try_get_ops(chip); > > > > - if (!rc) { > > > > - if (chip->flags & TPM_CHIP_FLAG_TPM2) { > > > > - tpm2_end_auth_session(chip); > > > > - tpm2_shutdown(chip, TPM2_SU_STATE); > > > > - } else { > > > > - rc = tpm1_pm_suspend(chip, tpm_suspend_pcr); > > > > - } > > > > - > > > > - tpm_put_ops(chip); > > > > + if (chip->flags & TPM_CHIP_FLAG_TPM2) { > > > > + tpm2_end_auth_session(chip); > > > > + tpm2_shutdown(chip, TPM2_SU_STATE); > > > > + goto suspended; > > > > } > > > > > > > > + rc = tpm1_pm_suspend(chip, tpm_suspend_pcr); > > > > + > > > > > > > > > I imagine the above still be wrapped in an else with the if (chip->flags > > > & TPM_CHIP_FLAG_TPM2) > > > otherwise it will call tpm1_pm_suspend for both tpm1 and tpm2 devices, > > > yes? > > > > > > So: > > > > > > if (chip->flags & TPM_CHIP_FLAG_TPM2) { > > > tpm2_end_auth_session(chip); > > > tpm2_shutdown(chip, TPM2_SU_STATE); > > > goto suspended; > > > } else { > > > rc = tpm1_pm_suspend(chip, tpm_suspend_pcr); > > > } > > > > > > > > > Other than that I think it looks good. > > > > It should be fine because after tpm2_shutdown() is called there is "goto > > suspended;". This is IMHO more readable as it matches the structure of > > previous exits before it. In future if this needs to be improved it will > > easier to move the logic to a helper function (e.g. __tpm_pm_suspend()) > > where gotos are substituted with return-statements. > > > > BR, Jarkko > > > > Heh, yep. > > Reviewed-by: Jerry Snitselaar <[email protected]>
Thanks! BR, Jarkko
