Re: [PATCH v2 2/2] KEYS: trusted: Reserve TPM for seal and unseal operations

On Mon, 2020-09-28 at 18:31 +0300, Jarkko Sakkinen wrote:

When TPM 2.0 trusted keys code was moved to the trusted keys subsystem, the operations were unwrapped from tpm_try_get_ops() and tpm_put_ops(), which are used to take temporarily the ownership of the TPM chip.

Fix this issue by introducting trusted_tpm_load() and trusted_tpm_new(), which wrap these operations.

Fixes: 2e19e10131a0 ("KEYS: trusted: Move TPM2 trusted keys code") Reported-by: "James E.J. Bottomley" < James.Bottomley@HansenPartnership.com> Cc: Sumit Garg sumit.garg@linaro.org Cc: David Howells dhowells@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com

---

drivers/char/tpm/tpm.h | 2 - include/linux/tpm.h | 10 ++- security/keys/trusted-keys/trusted_tpm1.c | 78 +++++++++++++++----

---

3 files changed, 62 insertions(+), 28 deletions(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h index 947d1db0a5cc..4338573a8d48 100644 --- a/drivers/char/tpm/tpm.h +++ b/drivers/char/tpm/tpm.h @@ -194,8 +194,6 @@ static inline void tpm_msleep(unsigned int delay_msec) int tpm_chip_start(struct tpm_chip *chip); void tpm_chip_stop(struct tpm_chip *chip); struct tpm_chip *tpm_find_get_ops(struct tpm_chip *chip); -__must_check int tpm_try_get_ops(struct tpm_chip *chip); -void tpm_put_ops(struct tpm_chip *chip); struct tpm_chip *tpm_chip_alloc(struct device *dev, const struct tpm_class_ops *ops); diff --git a/include/linux/tpm.h b/include/linux/tpm.h index 8f4ff39f51e7..0fe1cb5517ea 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -397,6 +397,8 @@ static inline u32 tpm2_rc_value(u32 rc) #if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE) extern int tpm_is_tpm2(struct tpm_chip *chip); +extern __must_check int tpm_try_get_ops(struct tpm_chip *chip); +extern void tpm_put_ops(struct tpm_chip *chip); extern int tpm_pcr_read(struct tpm_chip *chip, u32 pcr_idx, struct tpm_digest *digest); extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, @@ -410,7 +412,13 @@ static inline int tpm_is_tpm2(struct tpm_chip *chip) { return -ENODEV; }

+static inline int tpm_try_get_ops(struct tpm_chip *chip) +{

• return -ENODEV;

+} +static inline void tpm_put_ops(struct tpm_chip *chip) +{ +} static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, struct tpm_digest *digest) { diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c index c7b1701cdac5..c1dfc32c780b 100644 --- a/security/keys/trusted-keys/trusted_tpm1.c +++ b/security/keys/trusted-keys/trusted_tpm1.c @@ -950,6 +950,51 @@ static struct trusted_key_payload *trusted_payload_alloc(struct key *key) return p; } +static int trusted_tpm_load(struct tpm_chip *chip,

• 	    struct trusted_key_payload *payload,
  

• 	    struct trusted_key_options *options)
  

+{

• int ret;
• if (tpm_is_tpm2(chip)) {

• ret = tpm_try_get_ops(chip);
  

• if (!ret) {
  

• 	ret = tpm2_unseal_trusted(chip, payload,
  

options);

• 	tpm_put_ops(chip);
  

• }
  

• } else {

• ret = key_unseal(payload, options);
  

• }
• return ret;

+}

+static int trusted_tpm_new(struct tpm_chip *chip,

• 	   struct trusted_key_payload *payload,
  

• 	   struct trusted_key_options *options)
  

+{

• int ret;
• ret = tpm_get_random(chip, payload->key, payload->key_len);
• if (ret < 0)

• return ret;
  

• if (ret != payload->key_len)

• return -EIO;
  

• if (tpm_is_tpm2(chip)) {

• ret = tpm_try_get_ops(chip);
  

• if (!ret) {
  

• 	ret = tpm2_seal_trusted(chip, payload,
  

options);

• 	tpm_put_ops(chip);
  

• }
  

• } else {

• ret = key_seal(payload, options);
  

• }
• return ret;

+}

/*

• trusted_instantiate - create a new trusted key

@@ -968,12 +1013,6 @@ static int trusted_instantiate(struct key *key, char *datablob; int ret = 0; int key_cmd;

• size_t key_len;
• int tpm2;
• tpm2 = tpm_is_tpm2(chip);
• if (tpm2 < 0)

• return tpm2;
  

if (datalen <= 0 || datalen > 32767 || !prep->data) return -EINVAL; @@ -1011,32 +1050,21 @@ static int trusted_instantiate(struct key *key, switch (key_cmd) { case Opt_load:

• if (tpm2)
  

• 	ret = tpm2_unseal_trusted(chip, payload,
  

options);

• else
  

• 	ret = key_unseal(payload, options);
  

• ret = trusted_tpm_load(chip, payload, options);
  

• dump_payload(payload); dump_options(options);
• if (ret < 0)

• 	pr_info("trusted_key: key_unseal failed
  

(%d)\n", ret);

• 	pr_info("%s: load failed (%d)\n", __func__,
  

ret);

• break; case Opt_new:

• key_len = payload->key_len;
  

• ret = tpm_get_random(chip, payload->key, key_len);
  

• if (ret < 0)
  

• 	goto out;
  

• ret = trusted_tpm_new(chip, payload, options);
  

• if (ret != key_len) {
  

• 	pr_info("trusted_key: key_create failed
  

(%d)\n", ret);

• 	ret = -EIO;
  

• 	goto out;
  

• }
  

• if (tpm2)
  

• 	ret = tpm2_seal_trusted(chip, payload,
  

options);

• else
  

• 	ret = key_seal(payload, options);
  

  if (ret < 0)

• 	pr_info("trusted_key: key_seal failed (%d)\n",
  

ret);

• 	pr_info("%s: new failed (%d)\n", __func__,
  

ret);

• break; default: ret = -EINVAL;

You didn't actually test this, did you? It trips over the double tpm_try_get_ops, once above then again in tpm_send. This is the hang:

[<0>] tpm_try_get_ops+0x3b/0x80 [<0>] tpm_find_get_ops+0x14/0x50 [<0>] tpm_send+0x23/0x80 [<0>] tpm2_seal_trusted+0x4b0/0x6c0 [trusted] [<0>] trusted_instantiate+0x353/0x3a0 [trusted] [<0>] __key_instantiate_and_link+0x50/0x160 [<0>] key_create_or_update+0x438/0x520 [<0>] __x64_sys_add_key+0x102/0x1f0 [<0>] do_syscall_64+0x33/0x80 [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

You need to replace all the tpm_send's in the code with tpm_transmit_cmd.

James