linux-kernel - [PATCH next] tpm: Fix a possible dereference of ERR_PTR in tpm

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Date:   Mon, 20 Mar 2023 23:14:15 -0700
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     error27@...il.com,
        Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH next] tpm: Fix a possible dereference of ERR_PTR in tpm_init()

Smatch reports:
	drivers/char/tpm/tpm-interface.c:470 tpm_init() error:
	'tpm_class' dereferencing possible ERR_PTR()

If class_create() returns error pointer, we are dereferencing a possible
error pointer. Fix this by moving the dereference post error handling.

Fixes: a010eb881243 ("tpm: fix up the tpm_class shutdown_pre pointer when created")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
---
This is based on static analysis, only compile tested.
---
 drivers/char/tpm/tpm-interface.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 43e23a04433a..4463d0018290 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -467,12 +467,13 @@ static int __init tpm_init(void)
 	int rc;
 
 	tpm_class = class_create("tpm");
-	tpm_class->shutdown_pre = tpm_class_shutdown;
 	if (IS_ERR(tpm_class)) {
 		pr_err("couldn't create tpm class\n");
 		return PTR_ERR(tpm_class);
 	}
 
+	tpm_class->shutdown_pre = tpm_class_shutdown;
+
 	tpmrm_class = class_create("tpmrm");
 	if (IS_ERR(tpmrm_class)) {
 		pr_err("couldn't create tpmrm class\n");
-- 
2.38.1