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

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Message-ID: <20230329215903.632cn3lrkpi3lz2p@kernel.org>
Date:   Thu, 30 Mar 2023 00:59:03 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Cc:     error27@...il.com, Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] tpm: Fix a possible dereference of ERR_PTR in
 tpm_init()

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@...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
> 


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

BR, Jarkko