[PATCH] Keys: Remove redundant initialization of cred

[PATCH] Keys: Remove redundant initialization of cred

[Yang Li]

Pointer cred is being initialized however this value is never
read as cred is assigned an updated value from the returned
call to get_current_cred(). Remove the redundant initialization.

Cleans up clang warning:

security/keys/request_key.c:119:21: warning: Value stored to 'cred'
during its initialization is never read
[clang-analyzer-deadcode.DeadStores]

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Fixes: 'commit bb952bb98a7e ("CRED: Separate per-task-group keyrings from signal_struct")'
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
---
 security/keys/request_key.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 2da4404..873c31f 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -116,7 +116,7 @@ static int call_sbin_request_key(struct key *authkey, void *aux)
 {
 	static char const request_key[] = "/sbin/request-key";
 	struct request_key_auth *rka = get_request_key_auth(authkey);
-	const struct cred *cred = current_cred();
+	const struct cred *cred;
 	key_serial_t prkey, sskey;
 	struct key *key = rka->target_key, *keyring, *session, *user_session;
 	char *argv[9], *envp[3], uid_str[12], gid_str[12];
-- 
1.8.3.1

Re: [PATCH] Keys: Remove redundant initialization of cred

[Jarkko Sakkinen]

On Sat, May 08, 2021 at 05:51:21PM +0800, Yang Li wrote:
> Pointer cred is being initialized however this value is never
> read as cred is assigned an updated value from the returned
> call to get_current_cred(). Remove the redundant initialization.
> 
> Cleans up clang warning:
> 
> security/keys/request_key.c:119:21: warning: Value stored to 'cred'
> during its initialization is never read
> [clang-analyzer-deadcode.DeadStores]
> 
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Fixes: 'commit bb952bb98a7e ("CRED: Separate per-task-group keyrings from signal_struct")'
> Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
> ---
>  security/keys/request_key.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/security/keys/request_key.c b/security/keys/request_key.c
> index 2da4404..873c31f 100644
> --- a/security/keys/request_key.c
> +++ b/security/keys/request_key.c
> @@ -116,7 +116,7 @@ static int call_sbin_request_key(struct key *authkey, void *aux)
>  {
>  	static char const request_key[] = "/sbin/request-key";
>  	struct request_key_auth *rka = get_request_key_auth(authkey);
> -	const struct cred *cred = current_cred();
> +	const struct cred *cred;
>  	key_serial_t prkey, sskey;
>  	struct key *key = rka->target_key, *keyring, *session, *user_session;
>  	char *argv[9], *envp[3], uid_str[12], gid_str[12];
> -- 
> 1.8.3.1
> 
> 

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

/Jarkko

Re: [PATCH] Keys: Remove redundant initialization of cred

[David Howells]

Yang Li <yang.lee@linux.alibaba.com> wrote:

> -	const struct cred *cred = current_cred();
> +	const struct cred *cred;

Good catch, but it's probably the wrong fix.

In that function, there is:

	const struct cred *cred = current_cred();
	...
	cred = get_current_cred();
	keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred, ...);
	put_cred(cred);
	...
	sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid));
	...

So we get the creds again, but with a ref, and then drop after calling
keyring_alloc()... and then access cred again, which is dodgy - but we get
away with it because cred is still pinned by our task_struct.

I think what is actually needed is to remove the get_current_cred() and the
put_cred() calls, in which case, you want this:

	Fixes: d84f4f992cbd ("CRED: Inaugurate COW credentials")

David