2021-05-08 09:53:13

by Yang Li

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

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 <[email protected]>
Fixes: 'commit bb952bb98a7e ("CRED: Separate per-task-group keyrings from signal_struct")'
Signed-off-by: Yang Li <[email protected]>
---
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

2021-05-09 20:48:23

by Jarkko Sakkinen

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

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 <[email protected]>
> Fixes: 'commit bb952bb98a7e ("CRED: Separate per-task-group keyrings from signal_struct")'
> Signed-off-by: Yang Li <[email protected]>
> ---
> 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 <[email protected]>

/Jarkko

2021-05-11 10:51:35

by David Howells

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

Yang Li <[email protected]> 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