tracehook: tracehook_tracer_task

This adds the tracehook_tracer_task() hook to consolidate all forms of
"Who is using ptrace on me?" logic.  This is used for "TracerPid:" in
/proc and for permission checks.  We also clean up the selinux code the
called an identical accessor.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a891fe4cb43b..4b74dba69a6d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -69,6 +69,7 @@
 #include <linux/mount.h>
 #include <linux/security.h>
 #include <linux/ptrace.h>
+#include <linux/tracehook.h>
 #include <linux/cgroup.h>
 #include <linux/cpuset.h>
 #include <linux/audit.h>
@@ -231,10 +232,14 @@ static int check_mem_permission(struct task_struct *task)
          * If current is actively ptrace'ing, and would also be
          * permitted to freshly attach with ptrace now, permit it.
          */
-        if (task->parent == current && (task->ptrace & PT_PTRACED) &&
-            task_is_stopped_or_traced(task) &&
-            ptrace_may_access(task, PTRACE_MODE_ATTACH))
-                return 0;
+        if (task_is_stopped_or_traced(task)) {
+                int match;
+                rcu_read_lock();
+                match = (tracehook_tracer_task(task) == current);
+                rcu_read_unlock();
+                if (match && ptrace_may_access(task, PTRACE_MODE_ATTACH))
+                        return 0;
+        }
 
         /*
          * Noone else is allowed.