Commit 8d6c83f0 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds

oom: __task_cred() need rcu_read_lock()

dump_tasks() needs to hold the RCU read lock around its access of the
target task's UID.  To this end it should use task_uid() as it only needs
that one thing from the creds.

The fact that dump_tasks() holds tasklist_lock is insufficient to prevent the
target process replacing its credentials on another CPU.

Then, this patch change to call rcu_read_lock() explicitly.

	===================================================
	[ INFO: suspicious rcu_dereference_check() usage. ]
	---------------------------------------------------
	mm/oom_kill.c:410 invoked rcu_dereference_check() without protection!

	other info that might help us debug this:

	rcu_scheduler_active = 1, debug_locks = 1
	4 locks held by kworker/1:2/651:
	 #0:  (events){+.+.+.}, at: [<ffffffff8106aae7>]
	process_one_work+0x137/0x4a0
	 #1:  (moom_work){+.+...}, at: [<ffffffff8106aae7>]
	process_one_work+0x137/0x4a0
	 #2:  (tasklist_lock){.+.+..}, at: [<ffffffff810fafd4>]
	out_of_memory+0x164/0x3f0
	 #3:  (&(&p->alloc_lock)->rlock){+.+...}, at: [<ffffffff810fa48e>]
	find_lock_task_mm+0x2e/0x70
Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b52723c5
...@@ -372,7 +372,7 @@ static void dump_tasks(const struct mem_cgroup *mem) ...@@ -372,7 +372,7 @@ static void dump_tasks(const struct mem_cgroup *mem)
} }
pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n", pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n",
task->pid, __task_cred(task)->uid, task->tgid, task->pid, task_uid(task), task->tgid,
task->mm->total_vm, get_mm_rss(task->mm), task->mm->total_vm, get_mm_rss(task->mm),
task_cpu(task), task->signal->oom_adj, task_cpu(task), task->signal->oom_adj,
task->signal->oom_score_adj, task->comm); task->signal->oom_score_adj, task->comm);
......
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