[patch 4/9] oom: Add missing rcu protection of __task_cred() indump_tasks

[Thomas Gleixner]

dump_tasks accesses __task_cred() without being in a RCU read side
critical section. tasklist_lock is not protecting that when
CONFIG_TREE_PREEMPT_RCU=y.

Add a rcu_read_lock/unlock() section around the code which accesses
__task_cred().

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
---
 mm/oom_kill.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6-tip/mm/oom_kill.c
===================================================================
--- linux-2.6-tip.orig/mm/oom_kill.c
+++ linux-2.6-tip/mm/oom_kill.c
@@ -329,10 +329,13 @@ static void dump_tasks(const struct mem_
 			task_unlock(p);
 			continue;
 		}
+		/* Protect __task_cred() access */
+		rcu_read_lock();
 		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d     %3d %s\n",
 		       p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm,
 		       get_mm_rss(mm), (int)task_cpu(p), p->signal->oom_adj,
 		       p->comm);
+		rcu_read_unlock();
 		task_unlock(p);
 	} while_each_thread(g, p);
 }


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