umh: creds: kill subprocess_info->cred logic

Now that nobody ever changes subprocess_info->cred we can kill this member
and related code.  ____call_usermodehelper() always runs in the context of
freshly forked kernel thread, it has the proper ->cred copied from its
parent kthread, keventd.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 0 insertions, 81 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 52507c3e1387..75c0fa881308 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -156,7 +156,6 @@ extern int copy_creds(struct task_struct *, unsigned long);
 extern struct cred *cred_alloc_blank(void);
 extern struct cred *prepare_creds(void);
 extern struct cred *prepare_exec_creds(void);
-extern struct cred *prepare_usermodehelper_creds(void);
 extern int commit_creds(struct cred *);
 extern void abort_creds(struct cred *);
 extern const struct cred *override_creds(const struct cred *);
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index d876dce217f0..6efd7a78de6a 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -56,7 +56,6 @@ enum umh_wait {
 struct subprocess_info {
         struct work_struct work;
         struct completion *complete;
-        struct cred *cred;
         char *path;
         char **argv;
         char **envp;
diff --git a/kernel/cred.c b/kernel/cred.c
index 2c24870c55d1..a2d5504fbcc2 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -347,66 +347,6 @@ struct cred *prepare_exec_creds(void)
 }
 
 /*
- * prepare new credentials for the usermode helper dispatcher
- */
-struct cred *prepare_usermodehelper_creds(void)
-{
-#ifdef CONFIG_KEYS
-        struct thread_group_cred *tgcred = NULL;
-#endif
-        struct cred *new;
-
-#ifdef CONFIG_KEYS
-        tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
-        if (!tgcred)
-                return NULL;
-#endif
-
-        new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
-        if (!new)
-                goto free_tgcred;
-
-        kdebug("prepare_usermodehelper_creds() alloc %p", new);
-
-        memcpy(new, &init_cred, sizeof(struct cred));
-
-        atomic_set(&new->usage, 1);
-        set_cred_subscribers(new, 0);
-        get_group_info(new->group_info);
-        get_uid(new->user);
-
-#ifdef CONFIG_KEYS
-        new->thread_keyring = NULL;
-        new->request_key_auth = NULL;
-        new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
-
-        atomic_set(&tgcred->usage, 1);
-        spin_lock_init(&tgcred->lock);
-        new->tgcred = tgcred;
-#endif
-
-#ifdef CONFIG_SECURITY
-        new->security = NULL;
-#endif
-        if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
-                goto error;
-        validate_creds(new);
-
-        BUG_ON(atomic_read(&new->usage) != 1);
-        return new;
-
-error:
-        put_cred(new);
-        return NULL;
-
-free_tgcred:
-#ifdef CONFIG_KEYS
-        kfree(tgcred);
-#endif
-        return NULL;
-}
-
-/*
  * Copy credentials for the new process created by fork()
  *
  * We share if we can, but under some circumstances we have to generate a new
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 743d3883517c..6194ec2f737b 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -134,8 +134,6 @@ static int ____call_usermodehelper(void *data)
         struct subprocess_info *sub_info = data;
         int retval;
 
-        BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
-
         /* Unblock all signals */
         spin_lock_irq(&current->sighand->siglock);
         flush_signal_handlers(current, 1);
@@ -143,10 +141,6 @@ static int ____call_usermodehelper(void *data)
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
-        /* Install the credentials */
-        commit_creds(sub_info->cred);
-        sub_info->cred = NULL;
-
         /* We can run anywhere, unlike our parent keventd(). */
         set_cpus_allowed_ptr(current, cpu_all_mask);
 
@@ -174,8 +168,6 @@ void call_usermodehelper_freeinfo(struct subprocess_info *info)
 {
         if (info->cleanup)
                 (*info->cleanup)(info);
-        if (info->cred)
-                put_cred(info->cred);
         kfree(info);
 }
 EXPORT_SYMBOL(call_usermodehelper_freeinfo);
@@ -231,8 +223,6 @@ static void __call_usermodehelper(struct work_struct *work)
         pid_t pid;
         enum umh_wait wait = sub_info->wait;
 
-        BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
-
         /* CLONE_VFORK: wait until the usermode helper has execve'd
          * successfully We need the data structures to stay around
          * until that is done.  */
@@ -355,12 +345,6 @@ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
         sub_info->path = path;
         sub_info->argv = argv;
         sub_info->envp = envp;
-        sub_info->cred = prepare_usermodehelper_creds();
-        if (!sub_info->cred) {
-                kfree(sub_info);
-                return NULL;
-        }
-
   out:
         return sub_info;
 }
@@ -411,9 +395,6 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info,
         DECLARE_COMPLETION_ONSTACK(done);
         int retval = 0;
 
-        BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
-        validate_creds(sub_info->cred);
-
         helper_lock();
         if (sub_info->path[0] == '\0')
                 goto out;