On Fri, Jun 10, 2022 at 01:08:37PM +0200, LinoSanfilippo@xxxxxx wrote:
> From: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
>
> The interrupt handler that sets the boolean variable irq_tested may run on
> another CPU as the thread that checks irq_tested as part of the irq test in
> tmp_tis_send().
>
> Since nothing guarantees cache coherency between CPUs for unsynchronized
> accesses to boolean variables the testing thread might not perceive the
> value change done in the interrupt handler.
>
> Avoid this issue by using a bitfield instead of a boolean variable and by
> accessing this field with the bit manipulating functions that provide cache
> coherency.
>
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
> ---
> drivers/char/tpm/tpm_tis_core.c | 13 +++++++------
> drivers/char/tpm/tpm_tis_core.h | 6 +++++-
> 2 files changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index dc56b976d816..6f2cf75add8b 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -470,7 +470,8 @@ static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
> int rc, irq;
> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>
> - if (!(chip->flags & TPM_CHIP_FLAG_IRQ) || priv->irq_tested)
> + if (!(chip->flags & TPM_CHIP_FLAG_IRQ) ||
> + test_bit(TPM_TIS_IRQ_TESTED, &priv->irqtest_flags))
> return tpm_tis_send_main(chip, buf, len);
>
> /* Verify receipt of the expected IRQ */
> @@ -480,11 +481,11 @@ static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
> rc = tpm_tis_send_main(chip, buf, len);
> priv->irq = irq;
> chip->flags |= TPM_CHIP_FLAG_IRQ;
> - if (!priv->irq_tested)
> + if (!test_bit(TPM_TIS_IRQ_TESTED, &priv->irqtest_flags))
> tpm_msleep(1);
> - if (!priv->irq_tested)
> + if (!test_bit(TPM_TIS_IRQ_TESTED, &priv->irqtest_flags))
> disable_interrupts(chip);
> - priv->irq_tested = true;
> + set_bit(TPM_TIS_IRQ_TESTED, &priv->irqtest_flags);
> return rc;
> }
>
> @@ -693,7 +694,7 @@ static irqreturn_t tis_int_handler(int dummy, void *dev_id)
> if (interrupt == 0)
> return IRQ_NONE;
>
> - priv->irq_tested = true;
> + set_bit(TPM_TIS_IRQ_TESTED, &priv->irqtest_flags);
> if (interrupt & TPM_INTF_DATA_AVAIL_INT)
> wake_up_interruptible(&priv->read_queue);
> if (interrupt & TPM_INTF_LOCALITY_CHANGE_INT)
> @@ -779,7 +780,7 @@ static int tpm_tis_probe_irq_single(struct tpm_chip *chip, u32 intmask,
> if (rc < 0)
> return rc;
>
> - priv->irq_tested = false;
> + clear_bit(TPM_TIS_IRQ_TESTED, &priv->irqtest_flags);
>
> /* Generate an interrupt by having the core call through to
> * tpm_tis_send
> diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> index 3be24f221e32..0f29d0b68c3e 100644
> --- a/drivers/char/tpm/tpm_tis_core.h
> +++ b/drivers/char/tpm/tpm_tis_core.h
> @@ -88,11 +88,15 @@ enum tpm_tis_flags {
> TPM_TIS_INVALID_STATUS = BIT(1),
> };
>
> +enum tpm_tis_irqtest_flags {
> + TPM_TIS_IRQ_TESTED = BIT(0),
> +};
> +
> struct tpm_tis_data {
> u16 manufacturer_id;
> int locality;
> int irq;
> - bool irq_tested;
> + unsigned long irqtest_flags;
> unsigned long flags;
> void __iomem *ilb_base_addr;
> u16 clkrun_enabled;
> --
> 2.36.1
>
Otherwise looks fine, but please add TPM_TIS_IRQ_TESTED to 'flags', and
convert existing sites to use set_bit() and and test_bit().
BR, Jarkko
