proc: task_state: ptrace_parent() doesn't need pid_alive() check

p->ptrace != 0 means that release_task(p) was not called, so pid_alive()
buys nothing and we can remove this check.  Other callers already use it
directly without additional checks.

Note: with or without this patch ptrace_parent() can return the pointer to
the freed task, this will be explained/fixed later.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Cc: Sterling Alexander <stalexan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roland McGrath <roland@hack.frob.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 7 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 800e30f8f284..bd117d065b82 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -157,19 +157,18 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
         struct user_namespace *user_ns = seq_user_ns(m);
         struct group_info *group_info;
         int g;
+        struct task_struct *tracer;
         const struct cred *cred;
-        pid_t ppid, tpid, tgid, ngid;
+        pid_t ppid, tpid = 0, tgid, ngid;
         unsigned int max_fds = 0;
 
         rcu_read_lock();
         ppid = pid_alive(p) ?
                 task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0;
-        tpid = 0;
-        if (pid_alive(p)) {
-                struct task_struct *tracer = ptrace_parent(p);
-                if (tracer)
-                        tpid = task_pid_nr_ns(tracer, ns);
-        }
+
+        tracer = ptrace_parent(p);
+        if (tracer)
+                tpid = task_pid_nr_ns(tracer, ns);
 
         tgid = task_tgid_nr_ns(p, ns);
         ngid = task_numa_group_id(p);