linux-kernel - [PATCH v2] tpm/eventlog: Don't abort tpm_read

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Date:   Wed,  8 Jun 2022 14:31:08 +0200
From:   Morten Linderud <morten@...derud.pw>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Morten Linderud <morten@...derud.pw>,
        Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] 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 the function returns -EIO
which would abort discovery of the eventlog.

This change ensure we always return -ENODEV in tpm_read_log_acpi() and
fallback to the EFI configuration table.

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

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()

---
 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 1b18ce5ebab1..2b15d6eebd69 100644
--- a/drivers/char/tpm/eventlog/acpi.c
+++ b/drivers/char/tpm/eventlog/acpi.c
@@ -136,8 +136,12 @@ 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);
 
-- 
2.36.1