linux-kernel - [PATCH] tpm: fix NPE on probe for missing device

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Date:   Thu, 23 Dec 2021 09:49:31 -0600
From:   Patrick Williams <patrick@...cx.xyz>
To:     Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Hao Wu <hao.wu@...rik.com>
Cc:     Patrick Williams <patrick@...cx.xyz>, stable@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] tpm: fix NPE on probe for missing device

When using the tpm_tis-spi driver on a system missing the physical TPM,
a null pointer exception was observed.

    [    0.938677] Unable to handle kernel NULL pointer dereference at virtual address 00000004
    [    0.939020] pgd = 10c753cb
    [    0.939237] [00000004] *pgd=00000000
    [    0.939808] Internal error: Oops: 5 [#1] SMP ARM
    [    0.940157] CPU: 0 PID: 48 Comm: kworker/u4:1 Not tainted 5.15.10-dd1e40c #1
    [    0.940364] Hardware name: Generic DT based system
    [    0.940601] Workqueue: events_unbound async_run_entry_fn
    [    0.941048] PC is at tpm_tis_remove+0x28/0xb4
    [    0.941196] LR is at tpm_tis_core_init+0x170/0x6ac

This is due to an attempt in 'tpm_tis_remove' to use the drvdata, which
was not initialized in 'tpm_tis_core_init' prior to the first error.

Move the initialization of drvdata earlier so 'tpm_tis_remove' has
access to it.

Signed-off-by: Patrick Williams <patrick@...cx.xyz>
Fixes: 79ca6f74dae0 ("tpm: fix Atmel TPM crash caused by too frequent queries")
Cc: stable@...r.kernel.org
---
 drivers/char/tpm/tpm_tis_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index b2659a4c4016..9813b934e6e4 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -950,6 +950,8 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
 	priv->timeout_max = TPM_TIMEOUT_USECS_MAX;
 	priv->phy_ops = phy_ops;
 
+	dev_set_drvdata(&chip->dev, priv);
+
 	rc = tpm_tis_read32(priv, TPM_DID_VID(0), &vendor);
 	if (rc < 0)
 		goto out_err;
@@ -962,8 +964,6 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
 		priv->timeout_max = TIS_TIMEOUT_MAX_ATML;
 	}
 
-	dev_set_drvdata(&chip->dev, priv);
-
 	if (is_bsw()) {
 		priv->ilb_base_addr = ioremap(INTEL_LEGACY_BLK_BASE_ADDR,
 					ILB_REMAP_SIZE);
-- 
2.32.0