Re: [LKP] [mm, oom] c1e4c54f9c: BUG:KASAN:null-ptr-deref_in_d

[David Rientjes]

On Mon, 6 Aug 2018, 禹舟键 wrote:

> Hi Michal
> Sorry, I cannot open the link you shared.
> 

The suggestion atop your previous patch was

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -438,14 +438,6 @@ static void dump_header(struct oom_control *oc, struct 
task_struct *p)
 
        dump_stack();
 
-       /* one line summary of the oom killer context. */
-       pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
-                       oom_constraint_text[oc->constraint],
-                       nodemask_pr_args(oc->nodemask));
-       cpuset_print_current_mems_allowed();
-       mem_cgroup_print_oom_context(oc->memcg, p);
-       pr_cont(",task=%s,pid=%d,uid=%d\n", p->comm, p->pid,
-               from_kuid(&init_user_ns, task_uid(p)));
        if (is_memcg_oom(oc))
                mem_cgroup_print_oom_meminfo(oc->memcg);
        else {
@@ -836,7 +828,8 @@ static bool task_will_free_mem(struct task_struct *task)
        return ret;
 }
 
-static void __oom_kill_process(struct task_struct *victim)
+static void __oom_kill_process(struct task_struct *victim,
+                              struct oom_control *oc)
 {
        struct task_struct *p;
        struct mm_struct *mm;
@@ -883,6 +876,18 @@ static void __oom_kill_process(struct task_struct *victim)
                K(get_mm_counter(victim->mm, MM_ANONPAGES)),
                K(get_mm_counter(victim->mm, MM_FILEPAGES)),
                K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
+
+       if (oc) {
+               /* One line summary for non-group oom kills */
+               pr_info("oom-kill: constraint=%s, nodemask=%*pbl",
+                       oom_constraint_text[oc->constraint],
+                       nodemask_pr_args(oc->nodemask));
+               cpuset_print_current_mems_allowed();
+               mem_cgroup_print_oom_context(oc->memcg, victim);
+               pr_cont(", task=%s, pid=%d, uid=%d\n",
+                       victim->comm, victim->pid,
+                       from_kuid(&init_user_ns, task_uid(victim)));
+       }
        task_unlock(victim);
 
        /*
@@ -986,13 +991,13 @@ static void oom_kill_process(struct oom_control *oc, 
const char *message)
        }
        read_unlock(&tasklist_lock);
 
-       __oom_kill_process(victim);
+       __oom_kill_process(victim, oc);
 }
 
 static int oom_kill_memcg_member(struct task_struct *task, void *unused)
 {
        get_task_struct(task);
-       __oom_kill_process(task);
+       __oom_kill_process(task, NULL);
        return 0;
 }
 
@@ -1020,7 +1025,7 @@ static bool oom_kill_memcg_victim(struct oom_control *oc)
                    oc->chosen_task == INFLIGHT_VICTIM)
                        goto out;
 
-               __oom_kill_process(oc->chosen_task);
+               __oom_kill_process(oc->chosen_task, oc);
        }
 
 out:


You should be able to find this in your email.  We don't want to emit the 
line when a victim is not chosen.  I also did a couple of cleanups like 
spaces between commas.