Re: [Qemu-devel] [PATCH 1/2] tpm: check localities index

[Marc-André Lureau]

Hi

On Tue, Nov 6, 2018 at 9:25 AM P J P <address@hidden> wrote:
>
> From: Prasad J Pandit <address@hidden>
>
> While performing mmio device r/w operations, guest could set 'addr'
> parameter such that 'locty' index exceeds TPM_TIS_NUM_LOCALITIES=5.
> Add check to avoid OOB access.
>

Unless memory_region_init_io() is broken, and the region size is >
TPM_TIS_NUM_LOCALITIES << TPM_TIS_LOCALITY_SHIFT, I don't see how that
could happen. Do you have a reproducer?

Perhaps replace the conditions with an assert instead?

> Reported-by: Cheng Feng <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
>  hw/tpm/tpm_tis.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/hw/tpm/tpm_tis.c b/hw/tpm/tpm_tis.c
> index 12f5c9a759..20126dd838 100644
> --- a/hw/tpm/tpm_tis.c
> +++ b/hw/tpm/tpm_tis.c
> @@ -293,6 +293,10 @@ static void tpm_tis_request_completed(TPMIf *ti, int ret)
>      uint8_t locty = s->cmd.locty;
>      uint8_t l;
>
> +    if (locty >= TPM_TIS_NUM_LOCALITIES) {
> +        return;
> +    }
> +
>      if (s->cmd.selftest_done) {
>          for (l = 0; l < TPM_TIS_NUM_LOCALITIES; l++) {
>              s->loc[locty].sts |= TPM_TIS_STS_SELFTEST_DONE;
> @@ -401,7 +405,8 @@ static uint64_t tpm_tis_mmio_read(void *opaque, hwaddr 
> addr,
>      uint32_t avail;
>      uint8_t v;
>
> -    if (tpm_backend_had_startup_error(s->be_driver)) {
> +    if (tpm_backend_had_startup_error(s->be_driver)
> +        || locty >= TPM_TIS_NUM_LOCALITIES) {
>          return 0;
>      }
>
> @@ -530,7 +535,8 @@ static void tpm_tis_mmio_write(void *opaque, hwaddr addr,
>          return;
>      }
>
> -    if (tpm_backend_had_startup_error(s->be_driver)) {
> +    if (tpm_backend_had_startup_error(s->be_driver)
> +        || locty >= TPM_TIS_NUM_LOCALITIES) {
>          return;
>      }
>
> --
> 2.17.2
>
>


-- 
Marc-André Lureau