[PATCH-for-7.1] hw/tpm/tpm_tis: Avoid eventual read overrun

Commit Message

Philippe Mathieu-Daudé March 30, 2022, 11:57 p.m. UTC

From: Philippe Mathieu-Daudé <[e-mail]>

The TPMState structure hold an array of TPM_TIS_NUM_LOCALITIES
TPMLocality loc[], having TPM_TIS_NUM_LOCALITIES defined as '5'.

tpm_tis_locality_from_addr() returns up to 3 bits, so 7.

While unlikely, Coverity is right to report an overrun. Assert
we are in range to fix:

  *** CID 1487240:  Memory - illegal accesses  (OVERRUN)
  hw/tpm/tpm_tis_common.c: 298 in tpm_tis_dump_state()
  294         int idx;
  295         uint8_t locty = tpm_tis_locality_from_addr(addr);
  296         hwaddr base = addr & ~0xfff;
  297
  >>>     CID 1487240:  Memory - illegal accesses  (OVERRUN)
  >>>     Overrunning array "s->loc" of 5 24-byte elements at element index 7 (byte offset 191) using index "locty" (which evaluates to 7).
  298         printf("tpm_tis: active locality      : %d\n"
  299                "tpm_tis: state of locality %d : %d\n"
  300                "tpm_tis: register dump:\n",
  301                s->active_locty,
  302                locty, s->loc[locty].state);

Fixes: Coverity CID 1487240
Signed-off-by: Philippe Mathieu-Daudé <[e-mail]>
---
 hw/tpm/tpm_tis_common.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Marc-André Lureau March 31, 2022, 7:50 a.m. UTC | #1

Hi

On Thu, Mar 31, 2022 at 4:02 AM Philippe Mathieu-Daudé <
[e-mail]> wrote:

> From: Philippe Mathieu-Daudé <[e-mail]>
>
> The TPMState structure hold an array of TPM_TIS_NUM_LOCALITIES
> TPMLocality loc[], having TPM_TIS_NUM_LOCALITIES defined as '5'.
>
> tpm_tis_locality_from_addr() returns up to 3 bits, so 7.
>
> While unlikely, Coverity is right to report an overrun. Assert
> we are in range to fix:
>
>   *** CID 1487240:  Memory - illegal accesses  (OVERRUN)
>   hw/tpm/tpm_tis_common.c: 298 in tpm_tis_dump_state()
>   294         int idx;
>   295         uint8_t locty = tpm_tis_locality_from_addr(addr);
>   296         hwaddr base = addr & ~0xfff;
>   297
>   >>>     CID 1487240:  Memory - illegal accesses  (OVERRUN)
>   >>>     Overrunning array "s->loc" of 5 24-byte elements at element
> index 7 (byte offset 191) using index "locty" (which evaluates to 7).
>   298         printf("tpm_tis: active locality      : %d\n"
>   299                "tpm_tis: state of locality %d : %d\n"
>   300                "tpm_tis: register dump:\n",
>   301                s->active_locty,
>   302                locty, s->loc[locty].state);
>
> Fixes: Coverity CID 1487240
> Signed-off-by: Philippe Mathieu-Daudé <[e-mail]>
>

Maybe that assert should be in tpm_tis_locality_from_addr(), as various
callers could produce the same report.


---
>  hw/tpm/tpm_tis_common.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/hw/tpm/tpm_tis_common.c b/hw/tpm/tpm_tis_common.c
> index e700d82181..5b1055033e 100644
> --- a/hw/tpm/tpm_tis_common.c
> +++ b/hw/tpm/tpm_tis_common.c
> @@ -295,6 +295,7 @@ static void tpm_tis_dump_state(TPMState *s, hwaddr
> addr)
>      uint8_t locty = tpm_tis_locality_from_addr(addr);
>      hwaddr base = addr & ~0xfff;
>
> +    assert(TPM_TIS_IS_VALID_LOCTY(locty));
>      printf("tpm_tis: active locality      : %d\n"
>             "tpm_tis: state of locality %d : %d\n"
>             "tpm_tis: register dump:\n",
> --
> 2.35.1
>
>
>

Philippe Mathieu-Daudé March 31, 2022, 10:42 a.m. UTC | #2

On 31/3/22 09:50, Marc-André Lureau wrote:
> Hi
> 
> On Thu, Mar 31, 2022 at 4:02 AM Philippe Mathieu-Daudé 
> <[e-mail] 
> <mailto:[e-mail]>> wrote:
> 
>     From: Philippe Mathieu-Daudé <[e-mail] <mailto:[e-mail]>>
> 
>     The TPMState structure hold an array of TPM_TIS_NUM_LOCALITIES
>     TPMLocality loc[], having TPM_TIS_NUM_LOCALITIES defined as '5'.
> 
>     tpm_tis_locality_from_addr() returns up to 3 bits, so 7.
> 
>     While unlikely, Coverity is right to report an overrun. Assert
>     we are in range to fix:
> 
>        *** CID 1487240:  Memory - illegal accesses  (OVERRUN)
>        hw/tpm/tpm_tis_common.c: 298 in tpm_tis_dump_state()
>        294         int idx;
>        295         uint8_t locty = tpm_tis_locality_from_addr(addr);
>        296         hwaddr base = addr & ~0xfff;
>        297
>        >>>     CID 1487240:  Memory - illegal accesses  (OVERRUN)
>        >>>     Overrunning array "s->loc" of 5 24-byte elements at
>     element index 7 (byte offset 191) using index "locty" (which
>     evaluates to 7).
>        298         printf("tpm_tis: active locality      : %d\n"
>        299                "tpm_tis: state of locality %d : %d\n"
>        300                "tpm_tis: register dump:\n",
>        301                s->active_locty,
>        302                locty, s->loc[locty].state);
> 
>     Fixes: Coverity CID 1487240
>     Signed-off-by: Philippe Mathieu-Daudé <[e-mail]
>     <mailto:[e-mail]>>
> 
> 
> Maybe that assert should be in tpm_tis_locality_from_addr(), as various 
> callers could produce the same report.

OK I see, tpm_tis_memory_ops handlers are safe because mapped as:

     memory_region_init_io(&s->mmio, obj, &tpm_tis_memory_ops,
                           s, "tpm-tis-mmio",
                           TPM_TIS_NUM_LOCALITIES <<
                           TPM_TIS_LOCALITY_SHIFT);

So invalid addresses are impossible from guest.

Patch

diff --git a/hw/tpm/tpm_tis_common.c b/hw/tpm/tpm_tis_common.c
index e700d82181..5b1055033e 100644
--- a/hw/tpm/tpm_tis_common.c
+++ b/hw/tpm/tpm_tis_common.c
@@ -295,6 +295,7 @@  static void tpm_tis_dump_state(TPMState *s, hwaddr addr)
     uint8_t locty = tpm_tis_locality_from_addr(addr);
     hwaddr base = addr & ~0xfff;
 
+    assert(TPM_TIS_IS_VALID_LOCTY(locty));
     printf("tpm_tis: active locality      : %d\n"
            "tpm_tis: state of locality %d : %d\n"
            "tpm_tis: register dump:\n",