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>

2 files changed, 16 insertions, 6 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 797d775e0354..0d6eb33597c6 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -80,6 +80,7 @@
 #include <linux/delayacct.h>
 #include <linux/seq_file.h>
 #include <linux/pid_namespace.h>
+#include <linux/tracehook.h>
 
 #include <asm/pgtable.h>
 #include <asm/processor.h>
@@ -168,8 +169,12 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
         rcu_read_lock();
         ppid = pid_alive(p) ?
                 task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0;
-        tpid = pid_alive(p) && p->ptrace ?
-                task_pid_nr_ns(rcu_dereference(p->parent), ns) : 0;
+        tpid = 0;
+        if (pid_alive(p)) {
+                struct task_struct *tracer = tracehook_tracer_task(p);
+                if (tracer)
+                        tpid = task_pid_nr_ns(tracer, ns);
+        }
         seq_printf(m,
                 "State:\t%s\n"
                 "Tgid:\t%d\n"
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.