[PATCH 0/3] Fix bugs related to TPM2 event log

This series of patches fixes a couple of issues related to TPM2
event logs, such as the disappearance of the TPM2 log on QEMU machines
running with UEFI (my fault) and a kernel fault due to an integer under-
flow when reading the TPM 2 log multiple times.

Regards,
   Stefan

Stefan Berger (3):
  tpm: efi: Use local variable for calculating final log size
  tpm: acpi: Check eventlog signature before using it
  tpm: vtpm_proxy: Avoid reading host log when using a virtual device

 drivers/char/tpm/eventlog/acpi.c   | 31 +++++++++++++++++++++++++++++-
 drivers/char/tpm/eventlog/common.c |  3 +++
 drivers/char/tpm/eventlog/efi.c    | 10 ++++++----
 3 files changed, 39 insertions(+), 5 deletions(-)

-- 
2.29.2

When tpm_read_log_efi was called multiple times, which happens when one
loads and unloads a TPM2 driver multiple times, then the global variable
efi_tpm_final_log_size will at some point become a negative number due
to the subtraction of final_events_preboot_size occurring each time. Use
a local_efi_tpm_final_log_size to avoid this integer underflow.

The following issue is now resolved:

Mar  8 15:35:12 hibinst kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Mar  8 15:35:12 hibinst kernel: Workqueue: tpm-vtpm vtpm_proxy_work [tpm_vtpm_proxy]
Mar  8 15:35:12 hibinst kernel: RIP: 0010:__memcpy+0x12/0x20
Mar  8 15:35:12 hibinst kernel: Code: 00 b8 01 00 00 00 85 d2 74 0a c7 05 44 7b ef 00 0f 00 00 00 c3 cc cc cc 66 66 90 66 90 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 <f3> 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 f3 a4
Mar  8 15:35:12 hibinst kernel: RSP: 0018:ffff9ac4c0fcfde0 EFLAGS: 00010206
Mar  8 15:35:12 hibinst kernel: RAX: ffff88f878cefed5 RBX: ffff88f878ce9000 RCX: 1ffffffffffffe0f
Mar  8 15:35:12 hibinst kernel: RDX: 0000000000000003 RSI: ffff9ac4c003bff9 RDI: ffff88f878cf0e4d
Mar  8 15:35:12 hibinst kernel: RBP: ffff9ac4c003b000 R08: 0000000000001000 R09: 000000007e9d6073
Mar  8 15:35:12 hibinst kernel: R10: ffff9ac4c003b000 R11: ffff88f879ad3500 R12: 0000000000000ed5
Mar  8 15:35:12 hibinst kernel: R13: ffff88f878ce9760 R14: 0000000000000002 R15: ffff88f77de7f018
Mar  8 15:35:12 hibinst kernel: FS:  0000000000000000(0000) GS:ffff88f87bd00000(0000) knlGS:0000000000000000
Mar  8 15:35:12 hibinst kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mar  8 15:35:12 hibinst kernel: CR2: ffff9ac4c003c000 CR3: 00000001785a6004 CR4: 0000000000060ee0
Mar  8 15:35:12 hibinst kernel: Call Trace:
Mar  8 15:35:12 hibinst kernel: tpm_read_log_efi+0x152/0x1a7
Mar  8 15:35:12 hibinst kernel: tpm_bios_log_setup+0xc8/0x1c0
Mar  8 15:35:12 hibinst kernel: tpm_chip_register+0x8f/0x260
Mar  8 15:35:12 hibinst kernel: vtpm_proxy_work+0x16/0x60 [tpm_vtpm_proxy]
Mar  8 15:35:12 hibinst kernel: process_one_work+0x1b4/0x370
Mar  8 15:35:12 hibinst kernel: worker_thread+0x53/0x3e0
Mar  8 15:35:12 hibinst kernel: ? process_one_work+0x370/0x370

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 drivers/char/tpm/eventlog/efi.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/eventlog/efi.c b/drivers/char/tpm/eventlog/efi.c
index 35229e5143ca..b6ffb5faf416 100644
--- a/drivers/char/tpm/eventlog/efi.c
+++ b/drivers/char/tpm/eventlog/efi.c

@@ -18,6 +18,7 @@ int tpm_read_log_efi(struct tpm_chip *chip)
 
 	struct efi_tcg2_final_events_table *final_tbl = NULL;
 	struct linux_efi_tpm_eventlog *log_tbl;
+	int local_efi_tpm_final_log_size;
 	struct tpm_bios_log *log;
 	u32 log_size;
 	u8 tpm_log_version;

@@ -80,10 +81,11 @@ int tpm_read_log_efi(struct tpm_chip *chip)
 		goto out;
 	}
 
-	efi_tpm_final_log_size -= log_tbl->final_events_preboot_size;
+	local_efi_tpm_final_log_size = efi_tpm_final_log_size -
+					log_tbl->final_events_preboot_size;
 
 	tmp = krealloc(log->bios_event_log,
-		       log_size + efi_tpm_final_log_size,
+		       log_size + local_efi_tpm_final_log_size,
 		       GFP_KERNEL);
 	if (!tmp) {
 		kfree(log->bios_event_log);

@@ -100,9 +102,9 @@ int tpm_read_log_efi(struct tpm_chip *chip)
 	 */
 	memcpy((void *)log->bios_event_log + log_size,
 	       final_tbl->events + log_tbl->final_events_preboot_size,
-	       efi_tpm_final_log_size);
+	       local_efi_tpm_final_log_size);
 	log->bios_event_log_end = log->bios_event_log +
-		log_size + efi_tpm_final_log_size;
+		log_size + local_efi_tpm_final_log_size;
 
 out:
 	memunmap(final_tbl);

-- 
2.29.2

Check the eventlog signature before using it. This avoids using an
empty log, as may be the case when QEMU created the ACPI tables,
rather than probing the EFI log next. This resolves an issue where
the EFI log was empty since an empty ACPI log was used.

Fixes: 85467f63a05c ("tpm: Add support for event log pointer found in TPM2 ACPI table")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 drivers/char/tpm/eventlog/acpi.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/eventlog/acpi.c b/drivers/char/tpm/eventlog/acpi.c
index 3633ed70f48f..b6bfd22e4a2f 100644
--- a/drivers/char/tpm/eventlog/acpi.c
+++ b/drivers/char/tpm/eventlog/acpi.c

@@ -41,6 +41,25 @@ struct acpi_tcpa {
 	};
 };
 
+/* check that the given log is indeed a TPM2 log */
+static int tpm_check_tpm2_log_header(void *bios_event_log, u64 len)
+{
+	struct tcg_efi_specid_event_head *efispecid;
+	struct tcg_pcr_event *event_header = bios_event_log;
+
+	if (len < sizeof(*event_header))
+		return 1;
+	len -= sizeof(*event_header);
+
+	efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
+	if (len < sizeof(*efispecid) ||
+	    memcmp(efispecid->signature, TCG_SPECID_SIG,
+		   sizeof(TCG_SPECID_SIG)))
+		return 1;
+
+	return 0;
+}
+
 /* read binary bios log */
 int tpm_read_log_acpi(struct tpm_chip *chip)
 {

@@ -52,6 +71,7 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
 	struct acpi_table_tpm2 *tbl;
 	struct acpi_tpm2_phy *tpm2_phy;
 	int format;
+	int ret;
 
 	log = &chip->log;
 

@@ -112,6 +132,7 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
 
 	log->bios_event_log_end = log->bios_event_log + len;
 
+	ret = -EIO;
 	virt = acpi_os_map_iomem(start, len);
 	if (!virt)
 		goto err;

@@ -119,11 +140,19 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
 	memcpy_fromio(log->bios_event_log, virt, len);
 
 	acpi_os_unmap_iomem(virt, len);
+
+	if (chip->flags & TPM_CHIP_FLAG_TPM2 &&
+	    tpm_check_tpm2_log_header(log->bios_event_log, len)) {
+		/* try EFI log next */
+		ret = -ENODEV;
+		goto err;
+	}
+
 	return format;
 
 err:
 	kfree(log->bios_event_log);
 	log->bios_event_log = NULL;
-	return -EIO;
+	return ret;
 
 }

-- 
2.29.2

Avoid allocating memory and reading the host log when a virtual device
is used since this log is of no use to that driver. A virtual
device can be identified through the flag TPM_CHIP_FLAG_VIRTUAL, which
is only set for the tpm_vtpm_proxy driver.

Fixes: 6f99612e2500 ("tpm: Proxy driver for supporting multiple emulated TPMs")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 drivers/char/tpm/eventlog/common.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/char/tpm/eventlog/common.c b/drivers/char/tpm/eventlog/common.c
index 7460f230bae4..8512ec76d526 100644
--- a/drivers/char/tpm/eventlog/common.c
+++ b/drivers/char/tpm/eventlog/common.c

@@ -107,6 +107,9 @@ void tpm_bios_log_setup(struct tpm_chip *chip)
 	int log_version;
 	int rc = 0;
 
+	if (chip->flags & TPM_CHIP_FLAG_VIRTUAL)
+		return;
+
 	rc = tpm_read_log(chip);
 	if (rc < 0)
 		return;

-- 
2.29.2

On Mon, Mar 08, 2021 at 10:19:52PM -0500, Stefan Berger wrote:

This starts to have so many weird locals that an inline comment here
in plain Enlighs would be nice explaining the calculation.

 
 	tmp = krealloc(log->bios_event_log,
-		       log_size + efi_tpm_final_log_size,
+		       log_size + local_efi_tpm_final_log_size,

Ditto.

Ditto.

 
 out:
 	memunmap(final_tbl);
-- 
2.29.2

I think this is good chance to improve the documentation a bit.

/Jarkko

On Mon, Mar 08, 2021 at 10:19:53PM -0500, Stefan Berger wrote:

/* Check that the given log is indeed a TPM2 log. */

+static int tpm_check_tpm2_log_header(void *bios_event_log, u64 len)

Just by this name does not give any clue what the function does.
"check" can refer to almost anything.

Perhaps just tpm_is_tpm2_log()?

+{
+	struct tcg_efi_specid_event_head *efispecid;
+	struct tcg_pcr_event *event_header = bios_event_log;

Please, reorder these declarations (reverse christmas tree).

+
+	if (len < sizeof(*event_header))
+		return 1;
+	len -= sizeof(*event_header);
+
+	efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
+	if (len < sizeof(*efispecid) ||
+	    memcmp(efispecid->signature, TCG_SPECID_SIG,
+		   sizeof(TCG_SPECID_SIG)))

Please never put memcmp() inside a conditional statement.

/Jarkko