Messages in this thread | | | Date | Fri, 30 Oct 2020 21:38:31 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v5 14/21] kprobes: Remove NMI context check |
| |
On Sat, 29 Aug 2020 22:02:36 +0900 Masami Hiramatsu <mhiramat@kernel.org> wrote:
> Since the commit 9b38cc704e84 ("kretprobe: Prevent triggering > kretprobe from within kprobe_flush_task") sets a dummy current > kprobe in the trampoline handler by kprobe_busy_begin/end(), > it is not possible to run a kretprobe pre handler in kretprobe > trampoline handler context even with the NMI. If the NMI interrupts > a kretprobe_trampoline_handler() and it hits a kretprobe, the > 2nd kretprobe will detect recursion correctly and it will be > skipped. > This means we have almost no double-lock issue on kretprobes by NMI. > > The last one point is in cleanup_rp_inst() which also takes > kretprobe_table_lock without setting up current kprobes. > So adding kprobe_busy_begin/end() there allows us to remove > in_nmi() check. > > The above commit applies kprobe_busy_begin/end() on x86, but > now all arch implementation are unified to generic one, we can > safely remove the in_nmi() check from arch independent code. >
So are you saying that lockdep is lying?
Kprobe smoke test: started
================================ WARNING: inconsistent lock state 5.10.0-rc1-test+ #29 Not tainted -------------------------------- inconsistent {INITIAL USE} -> {IN-NMI} usage. swapper/0/1 [HC1[1]:SC0[0]:HE0:SE1] takes: ffffffff82b07118 (&rp->lock){....}-{2:2}, at: pre_handler_kretprobe+0x4b/0x193 {INITIAL USE} state was registered at: lock_acquire+0x280/0x325 _raw_spin_lock+0x30/0x3f recycle_rp_inst+0x3f/0x86 __kretprobe_trampoline_handler+0x13a/0x177 trampoline_handler+0x48/0x57 kretprobe_trampoline+0x2a/0x4f kretprobe_trampoline+0x0/0x4f init_kprobes+0x193/0x19d do_one_initcall+0xf9/0x27e kernel_init_freeable+0x16e/0x2b6 kernel_init+0xe/0x109 ret_from_fork+0x22/0x30 irq event stamp: 1670 hardirqs last enabled at (1669): [<ffffffff811cc344>] slab_free_freelist_hook+0xb4/0xfd hardirqs last disabled at (1670): [<ffffffff81da0887>] exc_int3+0xae/0x10a softirqs last enabled at (1484): [<ffffffff82000352>] __do_softirq+0x352/0x38d softirqs last disabled at (1471): [<ffffffff81e00f82>] asm_call_irq_on_stack+0x12/0x20
other info that might help us debug this: Possible unsafe locking scenario:
CPU0 ---- lock(&rp->lock); <Interrupt> lock(&rp->lock);
*** DEADLOCK ***
no locks held by swapper/0/1.
stack backtrace: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.10.0-rc1-test+ #29 Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014 Call Trace: dump_stack+0x7d/0x9f print_usage_bug+0x1c0/0x1d3 lock_acquire+0x302/0x325 ? pre_handler_kretprobe+0x4b/0x193 ? stop_machine_from_inactive_cpu+0x120/0x120 _raw_spin_lock_irqsave+0x43/0x58 ? pre_handler_kretprobe+0x4b/0x193 pre_handler_kretprobe+0x4b/0x193 ? stop_machine_from_inactive_cpu+0x120/0x120 ? kprobe_target+0x1/0x16 kprobe_int3_handler+0xd0/0x109 exc_int3+0xb8/0x10a asm_exc_int3+0x31/0x40 RIP: 0010:kprobe_target+0x1/0x16 5d c3 cc RSP: 0000:ffffc90000033e00 EFLAGS: 00000246 RAX: ffffffff8110ea77 RBX: 0000000000000001 RCX: ffffc90000033cb4 RDX: 0000000000000231 RSI: 0000000000000000 RDI: 000000003ca57c35 RBP: ffffc90000033e20 R08: 0000000000000000 R09: ffffffff8111d207 R10: ffff8881002ab480 R11: ffff8881002ab480 R12: 0000000000000000 R13: ffffffff82a52af0 R14: 0000000000000200 R15: ffff888100331130 ? register_kprobe+0x43c/0x492 ? stop_machine_from_inactive_cpu+0x120/0x120 ? kprobe_target+0x1/0x16 ? init_test_probes+0x2c6/0x38a init_kprobes+0x193/0x19d ? debugfs_kprobe_init+0xb8/0xb8 do_one_initcall+0xf9/0x27e ? rcu_read_lock_sched_held+0x3e/0x75 ? init_mm_internals+0x27b/0x284 kernel_init_freeable+0x16e/0x2b6 ? rest_init+0x152/0x152 kernel_init+0xe/0x109 ret_from_fork+0x22/0x30 Kprobe smoke test: passed successfully
Config attached.
-- Steve [unhandled content-type:application/octet-stream] | |