Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for
find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns.
Assertion failed in sys_ioprio_get. The patch is fixing assertion
failure in ioprio_set as well.
===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
kernel/pid.c:419 invoked rcu_dereference_check() without protection!
rcu_scheduler_active = 1, debug_locks = 0
1 lock held by iotop/4254:
#0: (tasklist_lock){.?.?..}, at: [<ffffffff811104b4>] sys_ioprio_get+0x22/0x2da
stack backtrace:
Pid: 4254, comm: iotop Not tainted
Call Trace:
[<ffffffff810656f2>] lockdep_rcu_dereference+0xaa/0xb2
[<ffffffff81053c67>] find_task_by_pid_ns+0x4f/0x68
[<ffffffff81053c9d>] find_task_by_vpid+0x1d/0x1f
[<ffffffff811104e2>] sys_ioprio_get+0x50/0x2da
[<ffffffff81002182>] system_call_fastpath+0x16/0x1b
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
diff --git a/fs/ioprio.c b/fs/ioprio.c
index 748cfb9..666343d 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -113,8 +113,11 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
case IOPRIO_WHO_PROCESS:
if (!who)
p = current;
- else
+ else {
+ rcu_read_lock();
p = find_task_by_vpid(who);
+ rcu_read_unlock();
+ }
if (p)
ret = set_task_ioprio(p, ioprio);
break;
@@ -202,8 +205,11 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
case IOPRIO_WHO_PROCESS:
if (!who)
p = current;
- else
+ else {
+ rcu_read_lock();
p = find_task_by_vpid(who);
+ rcu_read_unlock();
+ }
if (p)
ret = get_task_ioprio(p);
break;
--
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