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: stable@xxxxxxxxxxxxxxx # v6.4+ > Fixes: 99d464506255 ("tpm: Prevent hwrng from activating during resume") > Reported-by: Mike Seo <mikeseohyungjin@xxxxxxxxx> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219383 > Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> > --- > 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/D59JAI6RR2CD.G5E5T4ZCZ49W@xxxxxxxxxx/ > --- > 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. > suspended: > chip->flags |= TPM_CHIP_FLAG_SUSPENDED; > + tpm_put_ops(chip); > > +out: > if (rc) > dev_err(dev, "Ignoring error %d while suspending\n", rc); > return 0; > @@ -440,11 +445,18 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max) > if (!chip) > return -ENODEV; > > + /* Give back zero bytes, as TPM chip has not yet fully resumed: */ > + if (chip->flags & TPM_CHIP_FLAG_SUSPENDED) { > + rc = 0; > + goto out; > + } > + > if (chip->flags & TPM_CHIP_FLAG_TPM2) > rc = tpm2_get_random(chip, out, max); > else > rc = tpm1_get_random(chip, out, max); > > +out: > tpm_put_ops(chip); > return rc; > } > -- > 2.47.0 >