linux-kernel - [PATCH v2] tpm: Don't make vendor check required for probe

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Date:   Mon, 21 Aug 2023 09:02:30 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     <jarkko@...nel.org>
CC:     <linux-integrity@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Mario Limonciello" <mario.limonciello@....com>,
        <stable@...r.kernel.org>, "Todd Brandt" <todd.e.brandt@...el.com>,
        Patrick Steinhardt <ps@....im>, "Ronan Pigott" <ronan@....ie>,
        Raymond Jay Golo <rjgolo@...il.com>
Subject: [PATCH v2] tpm: Don't make vendor check required for probe

The vendor check introduced by commit 554b841d4703 ("tpm: Disable RNG for
all AMD fTPMs") doesn't work properly on a number of Intel fTPMs.  On the
reported systems the TPM doesn't reply at bootup and returns back the
command code. This makes the TPM fail probe.

As this isn't crucial for anything but AMD fTPM and AMD fTPM works, check
the chip vendor and if it's not AMD don't run the checks.

Cc: stable@...r.kernel.org
Fixes: 554b841d4703 ("tpm: Disable RNG for all AMD fTPMs")
Reported-by: Todd Brandt <todd.e.brandt@...el.com>
Reported-by: Patrick Steinhardt <ps@....im>
Reported-by: Ronan Pigott <ronan@....ie>
Reported-by: Raymond Jay Golo <rjgolo@...il.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217804
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
v1->v2:
 * Check x86 vendor for AMD
---
 drivers/char/tpm/tpm_crb.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 9eb1a18590123..7faf670201ccc 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -465,8 +465,12 @@ static bool crb_req_canceled(struct tpm_chip *chip, u8 status)
 
 static int crb_check_flags(struct tpm_chip *chip)
 {
+	int ret = 0;
+#ifdef CONFIG_X86
 	u32 val;
-	int ret;
+
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
+		return ret;
 
 	ret = crb_request_locality(chip, 0);
 	if (ret)
@@ -481,6 +485,7 @@ static int crb_check_flags(struct tpm_chip *chip)
 
 release:
 	crb_relinquish_locality(chip, 0);
+#endif
 
 	return ret;
 }
-- 
2.34.1