fs/proc/array.c: allow reporting eip/esp for all coredumping threads

0a1eb2d ("fs/proc: Stop reporting eip and esp in /proc/PID/stat")
stopped reporting eip/esp and fd7d562 ("fs/proc: Report eip/esp in
/prod/PID/stat for coredumping") reintroduced the feature to fix a
regression with userspace core dump handlers (such as minicoredumper).

Because PF_DUMPCORE is only set for the primary thread, this didn't fix
the original problem for secondary threads.  Allow reporting the eip/esp
for all threads by checking for PF_EXITING as well.  This is set for all
the other threads when they are killed.  coredump_wait() waits for all the
tasks to become inactive before proceeding to invoke a core dumper.

Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Fixes: fd7d562 ("fs/proc: Report eip/esp in /prod/PID/stat for coredumping")
Signed-off-by: John Ogness <[email protected]>
Reported-by: Jan Luebbe <[email protected]>
Tested-by: Jan Luebbe <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/proc/array.c

@@ -462,7 +462,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 		 * a program is not able to use ptrace(2) in that case. It is
 		 * safe because the task has stopped executing permanently.
 		 */
-		if (permitted && (task->flags & PF_DUMPCORE)) {
+		if (permitted && (task->flags & (PF_EXITING|PF_DUMPCORE))) {
 			if (try_get_task_stack(task)) {
 				eip = KSTK_EIP(task);
 				esp = KSTK_ESP(task);