CRED: Wrap task credential accesses in the core kernel

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-audit@redhat.com
Cc: containers@lists.linux-foundation.org
Cc: linux-mm@kvack.org
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 8af10027514b..e06962132aaf 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -439,10 +439,11 @@ static void free_pi_state(struct futex_pi_state *pi_state)
 static struct task_struct * futex_find_get_task(pid_t pid)
 {
 	struct task_struct *p;
+	uid_t euid = current_euid();
 
 	rcu_read_lock();
 	p = find_task_by_vpid(pid);
-	if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
+	if (!p || (euid != p->euid && euid != p->uid))
 		p = ERR_PTR(-ESRCH);
 	else
 		get_task_struct(p);
@@ -1829,6 +1830,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
 {
 	struct robust_list_head __user *head;
 	unsigned long ret;
+	uid_t euid = current_euid();
 
 	if (!futex_cmpxchg_enabled)
 		return -ENOSYS;
@@ -1844,8 +1846,8 @@ sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
 		if (!p)
 			goto err_unlock;
 		ret = -EPERM;
-		if ((current->euid != p->euid) && (current->euid != p->uid) &&
-				!capable(CAP_SYS_PTRACE))
+		if (euid != p->euid && euid != p->uid &&
+		    !capable(CAP_SYS_PTRACE))
 			goto err_unlock;
 		head = p->robust_list;
 		rcu_read_unlock();