linux-kernel - [PATCH v3] tpm/eventlog: Don't abort tpm_read

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Message-Id: <20230215092552.3004363-1-morten@linderud.pw>
Date:   Wed, 15 Feb 2023 10:25:52 +0100
From:   Morten Linderud <morten@...derud.pw>
To:     linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        jgg@...pe.ca, jarkko@...nel.org, peterhuewe@....de
Cc:     Morten Linderud <morten@...derud.pw>,
        Erkki Eilonen <erkki@...rmetal.eu>
Subject: [PATCH v3] tpm/eventlog: Don't abort tpm_read_log on faulty ACPI address

tpm_read_log_acpi() should return -ENODEV when no eventlog from the ACPI
table is found. If the firmware vendor includes an invalid log address
we are unable to map from the ACPI memory and tpm_read_log() returns -EIO
which would abort discovery of the eventlog.

Change the return value from -EIO to -ENODEV when acpi_os_map_iomem()
fails to map the event log.

The following hardware was used to test this issue:
    Framework Laptop (Pre-production)
    BIOS: INSYDE Corp, Revision: 3.2
    TPM Device: NTC, Firmware Revision: 7.2

Dump of the faulty ACPI TPM2 table:
    [000h 0000   4]                    Signature : "TPM2"    [Trusted Platform Module hardware interface Table]
    [004h 0004   4]                 Table Length : 0000004C
    [008h 0008   1]                     Revision : 04
    [009h 0009   1]                     Checksum : 2B
    [00Ah 0010   6]                       Oem ID : "INSYDE"
    [010h 0016   8]                 Oem Table ID : "TGL-ULT"
    [018h 0024   4]                 Oem Revision : 00000002
    [01Ch 0028   4]              Asl Compiler ID : "ACPI"
    [020h 0032   4]        Asl Compiler Revision : 00040000

    [024h 0036   2]               Platform Class : 0000
    [026h 0038   2]                     Reserved : 0000
    [028h 0040   8]              Control Address : 0000000000000000
    [030h 0048   4]                 Start Method : 06 [Memory Mapped I/O]

    [034h 0052  12]            Method Parameters : 00 00 00 00 00 00 00 00 00 00 00 00
    [040h 0064   4]           Minimum Log Length : 00010000
    [044h 0068   8]                  Log Address : 000000004053D000

Fixes: 0cf577a03f21 ("tpm: Fix handling of missing event log")
Tested-By: Erkki Eilonen <erkki@...rmetal.eu>
Signed-off-by: Morten Linderud <morten@...derud.pw>

---

v2: Tweak commit message and opt to return -ENODEV instead of loosening up the
    if condition in tpm_read_log()

v3: Mention function name instead of "this" in the commit log. Added Tested-By
    and Fixes tags

---
 drivers/char/tpm/eventlog/acpi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/eventlog/acpi.c b/drivers/char/tpm/eventlog/acpi.c
index 0913d3eb8d51..cd266021d010 100644
--- a/drivers/char/tpm/eventlog/acpi.c
+++ b/drivers/char/tpm/eventlog/acpi.c
@@ -143,8 +143,12 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
 
 	ret = -EIO;
 	virt = acpi_os_map_iomem(start, len);
-	if (!virt)
+	if (!virt) {
+		dev_warn(&chip->dev, "%s: Failed to map ACPI memory\n", __func__);
+		/* try EFI log next */
+		ret = -ENODEV;
 		goto err;
+	}
 
 	memcpy_fromio(log->bios_event_log, virt, len);
 
-- 
2.39.1