linux-kernel - [PATCH] tpm: Ensure that tpm chip has ops to check if it's defective

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Date:   Thu, 22 Jun 2023 22:04:27 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     <peterhuewe@....de>, <jarkko@...nel.org>, <jgg@...pe.ca>
CC:     <linux-integrity@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Mario Limonciello" <mario.limonciello@....com>,
        Linux regressions mailing list <regressions@...ts.linux.dev>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Sachin Sant <sachinp@...ux.ibm.com>
Subject: [PATCH] tpm: Ensure that tpm chip has ops to check if it's defective

The ibmvtpm doesn't have `chip->ops` set, and so trying to check
if it's a defective AMD fTPM doesn't work.

Add an extra check to tpm_amd_is_rng_defective() to ensure the
TPM being checked has `chip->ops`.

Cc: Linux regressions mailing list <regressions@...ts.linux.dev>
Reported-by: Aneesh Kumar K. V <aneesh.kumar@...ux.ibm.com>
Reported-by: Sachin Sant <sachinp@...ux.ibm.com>
Link: https://lore.kernel.org/lkml/99B81401-DB46-49B9-B321-CF832B50CAC3@linux.ibm.com/
Tested-by: Sachin Sant <sachinp@...ux.ibm.com>
Fixes: bd8621ca1510 ("tpm: Add !tpm_amd_is_rng_defective() to the hwrng_unregister() call site")
Fixes: f1324bbc4011 ("tpm: disable hwrng for fTPM on some AMD designs")
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 drivers/char/tpm/tpm-chip.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index cd48033b804a..9ba433761e9a 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -524,6 +524,9 @@ static bool tpm_amd_is_rng_defective(struct tpm_chip *chip)
 	u64 version;
 	int ret;
 
+	if (!chip->ops)
+		return false;
+
 	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
 		return false;
 
-- 
2.34.1