On Fri, Jun 19, 2020 at 11:53 AM Peter Zijlstra <[email protected]> wrote: > > On Thu, Jun 18, 2020 at 02:17:15PM -0700, syzbot wrote: > > > INFO: trying to register non-static key. > > the code is fine but needs lockdep annotation. > > turning off the locking correctness validator. > > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.7.0-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 01/01/2011 > > Call Trace: > > <IRQ> > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0xf6/0x16e lib/dump_stack.c:118 > > assign_lock_key kernel/locking/lockdep.c:894 [inline] > > register_lock_class+0x1442/0x17e0 kernel/locking/lockdep.c:1206 > > arch_stack_walk+0x81/0xf0 arch/x86/kernel/stacktrace.c:25 > > lock_downgrade+0x720/0x720 kernel/locking/lockdep.c:4624 > > is_dynamic_key+0x1b0/0x1b0 kernel/locking/lockdep.c:1176 > > trace_hardirqs_off+0x50/0x1f0 kernel/trace/trace_preemptirq.c:83 > > __lock_acquire+0x101/0x6270 kernel/locking/lockdep.c:4259 > > save_stack+0x32/0x40 mm/kasan/common.c:50 > > So I'm thinking this is in fact: > > spin_lock_irqsave(&depot_lock, flags); > > from lib/stackdepot.c:stack_depot_save(), which has gone missing from > the stack due to tail-call optimizations. > > Now depot_lock is declared thusly: > > static DEFINE_SPINLOCK(depot_lock); > > and I'm trying to figure out how lockdep manages to conclude that isn't > static storage.... most odd.
Note there also was something wrong with the unwinder: https://syzkaller.appspot.com/x/log.txt?x=13f305a9100000 (or with something else in the kernel), so potentially it did not happen save_stack. In fact, Andrey just reverted this parsing of questionable frames in syzkaller: https://github.com/google/syzkaller/commit/4d2d1ebee3b65c404576d1c8573a0ec48b03b883 (was done because of what turned out to be ORC unwinder bug, which was fixed). So potentially we just need to close this is invalid now.
