CRED: Separate task security context from task_struct

Separate the task security context from task_struct.  At this point, the
security data is temporarily embedded in the task_struct with two pointers
pointing to it.

Note that the Alpha arch is altered as it refers to (E)UID and (E)GID in
entry.S via asm-offsets.

With comment fixes Signed-off-by: Marc Dionne <marc.c.dionne@gmail.com>

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 10 insertions, 9 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 937f6b5b2008..49849d12dd12 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -115,6 +115,8 @@ int ptrace_check_attach(struct task_struct *child, int kill)
 
 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 {
+        struct cred *cred = current->cred, *tcred = task->cred;
+
         /* May we inspect the given task?
          * This check is used both for attaching with ptrace
          * and for allowing access to sensitive information in /proc.
@@ -123,19 +125,18 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode)
          * because setting up the necessary parent/child relationship
          * or halting the specified task is impossible.
          */
-        uid_t uid;
-        gid_t gid;
+        uid_t uid = cred->uid;
+        gid_t gid = cred->gid;
         int dumpable = 0;
         /* Don't let security modules deny introspection */
         if (task == current)
                 return 0;
-        current_uid_gid(&uid, &gid);
-        if ((uid != task->euid ||
-             uid != task->suid ||
-             uid != task->uid  ||
-             gid != task->egid ||
-             gid != task->sgid ||
-             gid != task->gid) && !capable(CAP_SYS_PTRACE))
+        if ((uid != tcred->euid ||
+             uid != tcred->suid ||
+             uid != tcred->uid  ||
+             gid != tcred->egid ||
+             gid != tcred->sgid ||
+             gid != tcred->gid) && !capable(CAP_SYS_PTRACE))
                 return -EPERM;
         smp_rmb();
         if (task->mm)