proc: fix -ESRCH error when writing to /proc/$pid/coredump_filter
proc: fix -ESRCH error when writing to /proc/$pid/coredump_filter

Writing to /proc/$pid/coredump_filter always returns -ESRCH because commit
774636e19ed51 ("proc: convert to kstrto*()/kstrto*_from_user()") removed
the setting of ret after the get_proc_task call and incorrectly left it as
-ESRCH.  Instead, return 0 when successful.

Example breakage:

  echo 0 > /proc/self/coredump_filter
  bash: echo: write error: No such process

Fixes: 774636e19ed51 ("proc: convert to kstrto*()/kstrto*_from_user()")
Signed-off-by: Colin Ian King <d100aa70785e45ee8deab668147d941941915c21@canonical.com>
Acked-by: Kees Cook <50cb10d2be062154b17ab4d66a4eab34f1cf1c84@chromium.org>
Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org> [4.3+]
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs