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>

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 800e30f..bd117d0 100644 (file)
--- 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);