[PATCH 5] utrace: convert ptrace to use utrace_set_caps()

[Oleg Nesterov]

Convert ptrace to use utrace_set_caps(). ptrace_report_clone() uses
utrace_get_caps() and PT_UTRACED instead of parent->ptrace.

Henceforth task_struct->ptrace is only used for PT_UTRACED, and this
bit can be moved into ENGINE_EXTRA_FLAGS.

utrace_unsafe_exec() doesn't need to play with task->ptrace any longer.

---

 kernel/ptrace-utrace.c |   18 ++++++++----------
 kernel/utrace.c        |    6 ------
 2 files changed, 8 insertions(+), 16 deletions(-)

--- RHEL6/kernel/ptrace-utrace.c~5_CONVERT_PTRACE       2010-05-20 
12:40:50.000000000 +0200
+++ RHEL6/kernel/ptrace-utrace.c        2010-07-07 02:59:52.000000000 +0200
@@ -198,7 +198,7 @@ static inline int ptrace_set_events(stru
  * Attach a utrace engine for ptrace and set up its event mask.
  * Returns error code or 0 on success.
  */
-static int ptrace_attach_task(struct task_struct *tracee, int options)
+static int ptrace_attach_task(struct task_struct *tracee, int options, int 
caps)
 {
        struct utrace_engine *engine;
        int err;
@@ -295,13 +295,13 @@ static u32 ptrace_report_exit(u32 action
 }
 
 static void ptrace_clone_attach(struct task_struct *child,
-                               int options)
+                               int options, int caps)
 {
        struct task_struct *parent = current;
        struct task_struct *tracer;
        bool abort = true;
 
-       if (unlikely(ptrace_attach_task(child, options))) {
+       if (unlikely(ptrace_attach_task(child, options, caps))) {
                WARN_ON(1);
                return;
        }
@@ -309,7 +309,7 @@ static void ptrace_clone_attach(struct t
        write_lock_irq(&tasklist_lock);
        tracer = parent->parent;
        if (!(tracer->flags & PF_EXITING) && parent->ptrace) {
-               child->ptrace = parent->ptrace;
+               child->ptrace = PT_UTRACED;
                __ptrace_link(child, tracer);
                abort = false;
        }
@@ -351,7 +351,8 @@ static u32 ptrace_report_clone(u32 actio
         */
        if ((event && event != PTRACE_EVENT_VFORK_DONE) ||
                                (clone_flags & CLONE_PTRACE))
-               ptrace_clone_attach(child, ctx->options);
+               ptrace_clone_attach(child, ctx->options,
+                                       utrace_get_caps(engine));
 
        if (!event)
                return UTRACE_RESUME;
@@ -632,7 +633,7 @@ int ptrace_attach(struct task_struct *ta
        if (retval)
                goto unlock_creds;
 
-       retval = ptrace_attach_task(task, 0);
+       retval = ptrace_attach_task(task, 0, capable(CAP_SYS_PTRACE));
        if (unlikely(retval))
                goto unlock_creds;
 
@@ -643,9 +644,6 @@ int ptrace_attach(struct task_struct *ta
 
        BUG_ON(task->ptrace);
        task->ptrace = PT_UTRACED;
-       if (capable(CAP_SYS_PTRACE))
-               task->ptrace |= PT_PTRACE_CAP;
-
        __ptrace_link(task, current);
        send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
 
@@ -665,7 +663,7 @@ out:
 int ptrace_traceme(void)
 {
        bool detach = true;
-       int ret = ptrace_attach_task(current, 0);
+       int ret = ptrace_attach_task(current, 0, 0);
 
        if (unlikely(ret))
                return ret;
--- RHEL6/kernel/utrace.c~5_CONVERT_PTRACE      2010-07-07 02:41:31.000000000 
+0200
+++ RHEL6/kernel/utrace.c       2010-07-07 19:16:19.000000000 +0200
@@ -2494,11 +2494,5 @@ int utrace_unsafe_exec(struct task_struc
        else if (task->utrace_flags & ENGINE_LSM_TRACE_CAP)
                unsafe = LSM_UNSAFE_PTRACE_CAP;
 
-       if (task->ptrace & PT_PTRACE_CAP) {
-               if (!unsafe)
-                       unsafe = LSM_UNSAFE_PTRACE_CAP;
-       } else if (task->ptrace)
-               unsafe = LSM_UNSAFE_PTRACE;
-
        return unsafe;
 }