[PATCH next] keys: Replace strcpy(derived_buf, "AUTH_KEY") with strscpy(..., HASH_SIZE)

[Jarkko Sakkinen]

On Sat, Jun 06, 2026 at 09:26:03PM +0100, david.laight.linux at gmail.com wrote:
> From: David Laight <david.laight.linux at gmail.com>
> 
> derived_buf is guaranteed to be HASH_SIZE - and it is more than enough.
> The strscpy() degenerates into an memcpy() (as did the strcpy()).
> Do the same for the associated "ENC_KEY" copy.
> 
> Removes a possibly unbounded strcpy().
> 
> Signed-off-by: David Laight <david.laight.linux at gmail.com>
> ---
> This is one of a group of patches that remove potentially unbounded
> strcpy() calls.
> 
> They are mostly replaced by strscpy() or, when strlen() has just been
> called, with memcpy() (usually including the '\0').
> 
> Calls with copy string literals into arrays are left unchanged.
> They are safe and easily detected as such.
> 
> The changes were made by getting the compiler to detect the calls and
> then fixing the code by hand.
> 
> Note that all the changes are only compile tested.
> 
> Some Makefiles were changed to allow files to contain strcpy().
> As well as 'difficult to fix' files, this included 'show' functions
> as they really need to use sysfs_emit() or seq_printf().
> 
> All the patches are being sent individually to avoid very long cc lists.
> Apologies for the terse commit messages and likely unexpected tags.
> (There are about 100 patches in total.)
> 
>  security/keys/encrypted-keys/encrypted.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
> index 56b531587a1e..59cb77b237b3 100644
> --- a/security/keys/encrypted-keys/encrypted.c
> +++ b/security/keys/encrypted-keys/encrypted.c
> @@ -343,9 +343,9 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
>  		return -ENOMEM;
>  
>  	if (key_type)
> -		strcpy(derived_buf, "AUTH_KEY");
> +		strscpy(derived_buf, "AUTH_KEY", HASH_SIZE);
>  	else
> -		strcpy(derived_buf, "ENC_KEY");
> +		strscpy(derived_buf, "ENC_KEY", HASH_SIZE);
>  
>  	memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
>  	       master_keylen);
> -- 
> 2.39.5
> 

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

BR, Jarkko