Messages in this thread Patch in this message | | | Date | Wed, 24 Nov 2010 19:33:39 -0500 | From | Dave Jones <> | Subject | rcu_read_lock/unlock protect find_task_by_vpid call in migrate_pages |
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=================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/pid.c:419 invoked rcu_dereference_check() without protection!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 1 1 lock held by scrashme/11079: #0: (tasklist_lock){.?.?..}, at: [<ffffffff81112702>] sys_migrate_pages+0xd6/0x29d
stack backtrace: Pid: 11079, comm: scrashme Not tainted 2.6.37-rc3+ #2 Call Trace: [<ffffffff8107d095>] lockdep_rcu_dereference+0x9d/0xa5 [<ffffffff81069dc8>] find_task_by_pid_ns+0x44/0x5d [<ffffffff81069e03>] find_task_by_vpid+0x22/0x24 [<ffffffff8111270f>] sys_migrate_pages+0xe3/0x29d [<ffffffff8107c7c6>] ? trace_hardirqs_off_caller+0xa3/0x10b [<ffffffff8147b635>] ? retint_swapgs+0x13/0x1b [<ffffffff8107e2e7>] ? trace_hardirqs_on_caller+0x13f/0x172 [<ffffffff8147a95c>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff81009cb2>] system_call_fastpath+0x16/0x1b
Signed-off-by: Dave Jones <davej@redhat.com>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 4a57f13..2f0f55b 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1308,6 +1308,7 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode, /* Find the mm_struct */ read_lock(&tasklist_lock); + rcu_read_lock(); task = pid ? find_task_by_vpid(pid) : current; if (!task) { read_unlock(&tasklist_lock); @@ -1315,6 +1316,7 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode, goto out; } mm = get_task_mm(task); + rcu_read_unlock(); read_unlock(&tasklist_lock); err = -EINVAL;
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