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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 5.7 38/58] tpm: Require that all digests are present in TCG_PCR_EVENT2 structures
Date: Sat,  8 Aug 2020 19:37:04 -0400
Message-ID: <20200808233724.3618168-38-sashal@kernel.org> (raw)
In-Reply-To: <20200808233724.3618168-1-sashal@kernel.org>

From: Tyler Hicks <tyhicks@linux.microsoft.com>

[ Upstream commit 7f3d176f5f7e3f0477bf82df0f600fcddcdcc4e4 ]

Require that the TCG_PCR_EVENT2.digests.count value strictly matches the
value of TCG_EfiSpecIdEvent.numberOfAlgorithms in the event field of the
TCG_PCClientPCREvent event log header. Also require that
TCG_EfiSpecIdEvent.numberOfAlgorithms is non-zero.

The TCG PC Client Platform Firmware Profile Specification section 9.1
(Family "2.0", Level 00 Revision 1.04) states:

 For each Hash algorithm enumerated in the TCG_PCClientPCREvent entry,
 there SHALL be a corresponding digest in all TCG_PCR_EVENT2 structures.
 Note: This includes EV_NO_ACTION events which do not extend the PCR.

Section 9.4.5.1 provides this description of
TCG_EfiSpecIdEvent.numberOfAlgorithms:

 The number of Hash algorithms in the digestSizes field. This field MUST
 be set to a value of 0x01 or greater.

Enforce these restrictions, as required by the above specification, in
order to better identify and ignore invalid sequences of bytes at the
end of an otherwise valid TPM2 event log. Firmware doesn't always have
the means necessary to inform the kernel of the actual event log size so
the kernel's event log parsing code should be stringent when parsing the
event log for resiliency against firmware bugs. This is true, for
example, when firmware passes the event log to the kernel via a reserved
memory region described in device tree.

POWER and some ARM systems use the "linux,sml-base" and "linux,sml-size"
device tree properties to describe the memory region used to pass the
event log from firmware to the kernel. Unfortunately, the
"linux,sml-size" property describes the size of the entire reserved
memory region rather than the size of the event long within the memory
region and the event log format does not include information describing
the size of the event log.

tpm_read_log_of(), in drivers/char/tpm/eventlog/of.c, is where the
"linux,sml-size" property is used. At the end of that function,
log->bios_event_log_end is pointing at the end of the reserved memory
region. That's typically 0x10000 bytes offset from "linux,sml-base",
depending on what's defined in the device tree source.

The firmware event log only fills a portion of those 0x10000 bytes and
the rest of the memory region should be zeroed out by firmware. Even in
the case of a properly zeroed bytes in the remainder of the memory
region, the only thing allowing the kernel's event log parser to detect
the end of the event log is the following conditional in
__calc_tpm2_event_size():

        if (event_type == 0 && event_field->event_size == 0)
                size = 0;

If that wasn't there, __calc_tpm2_event_size() would think that a 16
byte sequence of zeroes, following an otherwise valid event log, was
a valid event.

However, problems can occur if a single bit is set in the offset
corresponding to either the TCG_PCR_EVENT2.eventType or
TCG_PCR_EVENT2.eventSize fields, after the last valid event log entry.
This could confuse the parser into thinking that an additional entry is
present in the event log and exposing this invalid entry to userspace in
the /sys/kernel/security/tpm0/binary_bios_measurements file. Such
problems have been seen if firmware does not fully zero the memory
region upon a warm reboot.

This patch significantly raises the bar on how difficult it is for
stale/invalid memory to confuse the kernel's event log parser but
there's still, ultimately, a reliance on firmware to properly initialize
the remainder of the memory region reserved for the event log as the
parser cannot be expected to detect a stale but otherwise properly
formatted firmware event log entry.

Fixes: fd5c78694f3f ("tpm: fix handling of the TPM 2.0 event logs")
Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/tpm_eventlog.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
index 96d36b7a13440..6f1d1b7f8b429 100644
--- a/include/linux/tpm_eventlog.h
+++ b/include/linux/tpm_eventlog.h
@@ -211,9 +211,16 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
 
 	efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
 
-	/* Check if event is malformed. */
+	/*
+	 * Perform validation of the event in order to identify malformed
+	 * events. This function may be asked to parse arbitrary byte sequences
+	 * immediately following a valid event log. The caller expects this
+	 * function to recognize that the byte sequence is not a valid event
+	 * and to return an event size of 0.
+	 */
 	if (memcmp(efispecid->signature, TCG_SPECID_SIG,
-		   sizeof(TCG_SPECID_SIG)) || count > efispecid->num_algs) {
+		   sizeof(TCG_SPECID_SIG)) ||
+	    !efispecid->num_algs || count != efispecid->num_algs) {
 		size = 0;
 		goto out;
 	}
-- 
2.25.1


  parent reply index

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-08 23:36 [PATCH AUTOSEL 5.7 01/58] ARM: dts: stm32: fix uart7_pins_a comments in stm32mp15-pinctrl Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 02/58] x86/mce/inject: Fix a wrong assignment of i_mce.status Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 03/58] perf/x86/intel/uncore: Fix oops when counting IMC uncore events on some TGL Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 04/58] x86, sched: Bail out of frequency invariance if turbo frequency is unknown Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 05/58] x86, sched: Bail out of frequency invariance if turbo_freq/base_freq gives 0 Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 06/58] sched/fair: Fix NOHZ next idle balance Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 07/58] sched: correct SD_flags returned by tl->sd_flags() Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 08/58] arm64: dts: rockchip: fix rk3368-lion gmac reset gpio Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 09/58] arm64: dts: rockchip: fix rk3399-puma vcc5v0-host gpio Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 10/58] arm64: dts: rockchip: fix rk3399-puma gmac reset gpio Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 11/58] EDAC: Fix reference count leaks Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 12/58] crc-t10dif: Fix potential crypto notify dead-lock Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 13/58] arm64: dts: qcom: msm8916: Replace invalid bias-pull-none property Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 14/58] memory: tegra: Fix an error handling path in tegra186_emc_probe() Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 15/58] blktrace: fix debugfs use after free Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 16/58] crypto: ccree - fix resource leak on error path Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 17/58] ARM: exynos: MCPM: Restore big.LITTLE cpuidle support Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 18/58] rcu/tree: Repeat the monitor if any free channel is busy Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 19/58] firmware: arm_scmi: Fix SCMI genpd domain probing Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 20/58] arm64: dts: sun50i-pinephone: dldo4 must not be >= 1.8V Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 21/58] arm64: dts: exynos: Fix silent hang after boot on Espresso Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 22/58] sched/uclamp: Fix initialization of struct uclamp_rq Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 23/58] crypto: qat - allow xts requests not multiple of block Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 24/58] clk: scmi: Fix min and max rate when registering clocks with discrete rates Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 25/58] m68k: mac: Don't send IOP message until channel is idle Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 26/58] m68k: mac: Fix IOP status/control register writes Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 27/58] platform/x86: intel-hid: Fix return value check in check_acpi_dev() Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 28/58] platform/x86: intel-vbtn: " Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 29/58] ARM: dts: gose: Fix ports node name for adv7180 Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 30/58] arm64: dts: renesas: Fix SD Card/eMMC interface device node names Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 31/58] ARM: dts: gose: Fix ports node name for adv7612 Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 32/58] ARM: at91: pm: add missing put_device() call in at91_pm_sram_init() Sasha Levin
2020-08-08 23:36 ` [PATCH AUTOSEL 5.7 33/58] ARM: dts: exynos: Disable frequency scaling for FSYS bus on Odroid XU3 family Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 34/58] reset: intel: fix a compile warning about REG_OFFSET redefined Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 35/58] ARM: dts: sunxi: bananapi-m2-plus-v1.2: Add regulator supply to all CPU cores Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 36/58] ARM: dts: sunxi: bananapi-m2-plus-v1.2: Fix CPU supply voltages Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 37/58] spi: lantiq: fix: Rx overflow error in full duplex mode Sasha Levin
2020-08-08 23:37 ` Sasha Levin [this message]
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 39/58] recordmcount: only record relocation of type R_AARCH64_CALL26 on arm64 Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 40/58] regulator: fix memory leak on error path of regulator_register() Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 41/58] io_uring: fix sq array offset calculation Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 42/58] arm64: dts: meson: fix mmc0 tuning error on Khadas VIM3 Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 43/58] soc: qcom: pdr: Reorder the PD state indication ack Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 44/58] spi: rockchip: Fix error in SPI slave pio read Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 45/58] ARM: socfpga: PM: add missing put_device() call in socfpga_setup_ocram_self_refresh() Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 46/58] iocost: Fix check condition of iocg abs_vdebt Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 47/58] scripts/selinux/mdp: fix initial SID handling Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 48/58] irqchip/ti-sci-inta: Fix return value about devm_ioremap_resource() Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 49/58] seccomp: Fix ioctl number for SECCOMP_IOCTL_NOTIF_ID_VALID Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 50/58] md: raid0/linear: fix dereference before null check on pointer mddev Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 51/58] irqchip/loongson-liointc: Fix potential dead lock Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 52/58] irqchip/irq-bcm7038-l1: Guard uses of cpu_logical_map Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 53/58] irqchip/gic-v4.1: Use GFP_ATOMIC flag in allocate_vpe_l1_table() Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 54/58] nvme-tcp: fix controller reset hang during traffic Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 55/58] nvme-rdma: " Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 56/58] nvme-multipath: fix logic for non-optimized paths Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 57/58] nvme-multipath: do not fall back to __nvme_find_path() " Sasha Levin
2020-08-08 23:37 ` [PATCH AUTOSEL 5.7 58/58] block: don't do revalidate zones on invalid devices Sasha Levin

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