BUG_ON(cred == current->cred);
BUG_ON(cred == current->real_cred);
- call_rcu(&cred->rcu, put_cred_rcu);
+ if (cred->non_rcu)
+ put_cred_rcu(&cred->rcu);
+ else
+ call_rcu(&cred->rcu, put_cred_rcu);
}
EXPORT_SYMBOL(__put_cred);
new->magic = CRED_MAGIC;
#endif
- if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
+ if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
goto error;
return new;
old = task->cred;
memcpy(new, old, sizeof(struct cred));
+ new->non_rcu = 0;
atomic_set(&new->usage, 1);
set_cred_subscribers(new, 0);
get_group_info(new->group_info);
new->security = NULL;
#endif
- if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
+ if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
goto error;
validate_creds(new);
return new;
if (task->mm)
set_dumpable(task->mm, suid_dumpable);
task->pdeath_signal = 0;
+ /*
+ * If a task drops privileges and becomes nondumpable,
+ * the dumpability change must become visible before
+ * the credential change; otherwise, a __ptrace_may_access()
+ * racing with this change may be able to attach to a task it
+ * shouldn't be able to attach to (as if the task had dropped
+ * privileges without becoming nondumpable).
+ * Pairs with a read barrier in __ptrace_may_access().
+ */
smp_wmb();
}
validate_creds(old);
validate_creds(new);
- get_cred(new);
+
+ /*
+ * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
+ *
+ * That means that we do not clear the 'non_rcu' flag, since
+ * we are only installing the cred into the thread-synchronous
+ * '->cred' pointer, not the '->real_cred' pointer that is
+ * visible to other threads under RCU.
+ *
+ * Also note that we did validate_creds() manually, not depending
+ * on the validation in 'get_cred()'.
+ */
+ get_new_cred((struct cred *)new);
alter_cred_subscribers(new, 1);
rcu_assign_pointer(current->cred, new);
alter_cred_subscribers(old, -1);
}
/**
- * prepare_kernel_cred - Prepare a set of credentials for a kernel service
- * @daemon: A userspace daemon to be used as a reference
+ * clone_cred - Create a new copy of a set of credentials
+ * @old: Credentials to be copied
*
- * Prepare a set of credentials for a kernel service. This can then be used to
- * override a task's own credentials so that work can be done on behalf of that
- * task that requires a different subjective context.
+ * Prepare a new set of credentials that is an exact copy of @old. This can
+ * optionally be modified and used to override a task's own credentials so
+ * that work can be done on behalf of that task that requires a different
+ * subjective context.
*
- * @daemon is used to provide a base for the security record, but can be NULL.
- * If @daemon is supplied, then the security data will be derived from that;
- * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
- *
- * The caller may change these controls afterwards if desired.
- *
- * Returns the new credentials or NULL if out of memory.
+ * Returns the new credentials or NULL if @old is NULL or if out of memory.
*
* Does not take, and does not return holding current->cred_replace_mutex.
*/
-struct cred *prepare_kernel_cred(struct task_struct *daemon)
+struct cred *clone_cred(const struct cred *old)
{
- const struct cred *old;
struct cred *new;
+ if (!old)
+ return NULL;
+
new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
if (!new)
return NULL;
- kdebug("prepare_kernel_cred() alloc %p", new);
-
- if (daemon)
- old = get_task_cred(daemon);
- else
- old = get_cred(&init_cred);
+ kdebug("clone_cred() alloc %p", new);
validate_creds(old);
*new = *old;
+ new->non_rcu = 0;
atomic_set(&new->usage, 1);
set_cred_subscribers(new, 0);
get_uid(new->user);
#ifdef CONFIG_SECURITY
new->security = NULL;
#endif
- if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
+ if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
goto error;
- put_cred(old);
validate_creds(new);
return new;
error:
put_cred(new);
- put_cred(old);
return NULL;
}
+EXPORT_SYMBOL(clone_cred);
+
+/**
+ * prepare_kernel_cred - Prepare a set of credentials for a kernel service
+ * @daemon: A userspace daemon to be used as a reference
+ *
+ * Prepare a set of credentials for a kernel service. This can then be used to
+ * override a task's own credentials so that work can be done on behalf of that
+ * task that requires a different subjective context.
+ *
+ * @daemon is used to provide a base for the security record, but can be NULL.
+ * If @daemon is supplied, then the security data will be derived from that;
+ * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
+ *
+ * The caller may change these controls afterwards if desired.
+ *
+ * Returns the new credentials or NULL if out of memory.
+ *
+ * Does not take, and does not return holding current->cred_replace_mutex.
+ */
+struct cred *prepare_kernel_cred(struct task_struct *daemon)
+{
+ const struct cred *old;
+ struct cred *new;
+
+ if (daemon)
+ old = get_task_cred(daemon);
+ else
+ old = get_cred(&init_cred);
+
+ new = clone_cred(old);
+ put_cred(old);
+ return new;
+}
EXPORT_SYMBOL(prepare_kernel_cred);
/**
{
if (cred->magic != CRED_MAGIC)
return true;
-#ifdef CONFIG_SECURITY_SELINUX
- /*
- * cred->security == NULL if security_cred_alloc_blank() or
- * security_prepare_creds() returned an error.
- */
- if (selinux_is_enabled() && cred->security) {
- if ((unsigned long) cred->security < PAGE_SIZE)
- return true;
- if ((*(u32 *)cred->security & 0xffffff00) ==
- (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
- return true;
- }
-#endif
return false;
}
EXPORT_SYMBOL(creds_are_invalid);
projects / mirror_ubuntu-bionic-kernel.git / blobdiff