[PATCH next] tpm: Fix a possible dereference of ERR_PTR in tpm_init()

[PATCH next] tpm: Fix a possible dereference of ERR_PTR in tpm_init()

[Harshit Mogalapalli]

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@oracle.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

Re: [PATCH next] tpm: Fix a possible dereference of ERR_PTR in tpm_init()

[Greg Kroah-Hartman]

On Mon, Mar 20, 2023 at 11:14:15PM -0700, Harshit Mogalapalli wrote:
> 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@oracle.com>
> ---
> This is based on static analysis, only compile tested.

Thanks for this, good catch, I've queued it up in my tree now as I have
the offending change that caused this.

greg k-h

Re: [PATCH next] tpm: Fix a possible dereference of ERR_PTR in tpm_init()

[Jarkko Sakkinen]

On Mon, Mar 20, 2023 at 11:14:15PM -0700, Harshit Mogalapalli wrote:
> 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@oracle.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
> 


Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko

Re: [PATCH next] tpm: Fix a possible dereference of ERR_PTR in tpm_init()

[Jarkko Sakkinen]

On Tue, Mar 21, 2023 at 09:01:08AM +0100, Greg Kroah-Hartman wrote:
> On Mon, Mar 20, 2023 at 11:14:15PM -0700, Harshit Mogalapalli wrote:
> > 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@oracle.com>
> > ---
> > This is based on static analysis, only compile tested.
> 
> Thanks for this, good catch, I've queued it up in my tree now as I have
> the offending change that caused this.

OK, thank you!

BR, Jarkko