From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
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: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
mm/oom_kill.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 5014e50..7b03102 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -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",
- 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_cpu(task), task->signal->oom_adj,
task->signal->oom_score_adj, task->comm);
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