android,lowmemorykiller: Don't abuse TIF_MEMDIE.

[Dan Carpenter]

Hello Tetsuo Handa,

This is a semi-automatic email about new static checker warnings.

The patch 77ed2c5745d9: "android,lowmemorykiller: Don't abuse 
TIF_MEMDIE." from Mar 8, 2016, leads to the following Smatch 
complaint:

drivers/staging/android/lowmemorykiller.c:145 lowmem_scan()
	 error: we previously assumed 'p->mm' could be null (see line 134)

drivers/staging/android/lowmemorykiller.c
   133	
   134			if (task_lmk_waiting(p) && p->mm &&
                                                   ^^^^^
Patch adds a new check.

   135			    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
   136				task_unlock(p);
   137				rcu_read_unlock();
   138				return 0;
   139			}
   140			oom_score_adj = p->signal->oom_score_adj;
   141			if (oom_score_adj < min_score_adj) {
   142				task_unlock(p);
   143				continue;
   144			}
   145			tasksize = get_mm_rss(p->mm);
                                              ^^^^^
Old unchecked dereference inside function call.

   146			task_unlock(p);
   147			if (tasksize <= 0)

regards,
dan carpenter