linux-kernel - Re: [PATCH v2] s390/pkey: use kvfree_sensitive() to fix Coccinelle warning

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Date: Tue, 7 May 2024 15:53:32 +0200
From: Holger Dengler <dengler@...ux.ibm.com>
To: Jules Irenge <jbi.octave@...il.com>, svens@...ux.ibm.com
Cc: borntraeger@...ux.ibm.com, agordeev@...ux.ibm.com, gor@...ux.ibm.com,
        hca@...ux.ibm.com, freude@...ux.ibm.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] s390/pkey: use kvfree_sensitive() to fix Coccinelle
 warning

On 06/05/2024 19:21, Jules Irenge wrote:
> Replace memzero_expliocit() and kfree() with kvfree_sensitive() to fix
> warnings reported by Coccinelle

Thanks Jules for pointing that out. But instead of using kvfree_sensitive() I would recommend kfree_sensitive() here. We're not on a performance critical path so kfree_sensitive() would be in my opinion the better choice, because we don't need to take care about the right size.

> WARNING opportunity for kfree_sensitive/kvfree_sensitive (line 1506)
> WARNING opportunity for kfree_sensitive/kvfree_sensitive (line 1643)
> WARNING opportunity for kfree_sensitive/kvfree_sensitive (line 1770)
> 
> Signed-off-by: Jules Irenge <jbi.octave@...il.com>
> ---
> Changes in v2:
>  - merges all patches that fixe same problem into one
> 
>  drivers/s390/crypto/pkey_api.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/s390/crypto/pkey_api.c b/drivers/s390/crypto/pkey_api.c
> index dccf664a3d95..e1dd7e0bdfd4 100644
> --- a/drivers/s390/crypto/pkey_api.c
> +++ b/drivers/s390/crypto/pkey_api.c
> @@ -1503,8 +1503,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
>  		rc = pkey_keyblob2pkey(kkey, ktp.keylen, ktp.protkey.protkey,
>  				       &ktp.protkey.len, &ktp.protkey.type);
>  		pr_debug("%s pkey_keyblob2pkey()=%d\n", __func__, rc);
> -		memzero_explicit(kkey, ktp.keylen);
> -		kfree(kkey);
> +		kvfree_sensitive(kkey, ktp.keylen);

kfree_sensitive(kkey);

>  		if (rc)
>  			break;
>  		if (copy_to_user(utp, &ktp, sizeof(ktp)))
> @@ -1640,8 +1639,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
>  					&ktp.protkey.type);
>  		pr_debug("%s pkey_keyblob2pkey2()=%d\n", __func__, rc);
>  		kfree(apqns);
> -		memzero_explicit(kkey, ktp.keylen);
> -		kfree(kkey);
> +		kvfree_sensitive(kkey, ktp.keylen);

kfree_sensitive(kkey);

>  		if (rc)
>  			break;
>  		if (copy_to_user(utp, &ktp, sizeof(ktp)))
> @@ -1767,8 +1765,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
>  					protkey, &protkeylen, &ktp.pkeytype);
>  		pr_debug("%s pkey_keyblob2pkey3()=%d\n", __func__, rc);
>  		kfree(apqns);
> -		memzero_explicit(kkey, ktp.keylen);
> -		kfree(kkey);
> +		kvfree_sensitive(kkey, ktp.keylen);

kfree_sensitive(kkey);

>  		if (rc) {
>  			kfree(protkey);
>  			break;

-- 
Mit freundlichen Grüßen / Kind regards
Holger Dengler
--
IBM Systems, Linux on IBM Z Development
dengler@...ux.ibm.com