oom_kill: has_intersects_mems_allowed() needs rcu_read_lock()

oom_kill: has_intersects_mems_allowed() needs rcu_read_lock()

At least out_of_memory() calls has_intersects_mems_allowed() without
even rcu_read_lock(), this is obviously buggy.

Add the necessary rcu_read_lock().  This means that we can not simply
return from the loop, we need "bool ret" and "break".

While at it, swap the names of task_struct's (the argument and the
local).  This cleans up the code a little bit and avoids the unnecessary
initialization.

Signed-off-by: Oleg Nesterov <[email protected]>
Reviewed-by: Sergey Dyasly <[email protected]>
Tested-by: Sergey Dyasly <[email protected]>
Reviewed-by: Sameer Nanda <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Mandeep Singh Baines <[email protected]>
Cc: "Ma, Xindong" <[email protected]>
Reviewed-by: Michal Hocko <[email protected]>
Cc: "Tu, Xiaobing" <[email protected]>
Acked-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>