On 5/26/20 6:04 PM, Dongli Zhang wrote: > Hi Keith, > > On 5/25/20 9:45 AM, Keith Busch wrote: >> On Sun, May 24, 2020 at 07:33:02AM -0700, Dongli Zhang wrote: >>>>> After code analysis, I think this is for nvme-pci as well. >>>>> >>>>> nvme_process_cq() >>>>> -> nvme_handle_cqe() >>>>> -> nvme_end_request() >>>>> -> blk_mq_complete_request() >>>>> nvme_reset_work() >>>>> -> nvme_dev_disable() >>>>> -> nvme_reap_pending_cqes() >>>>> -> nvme_process_cq() >>>>> -> nvme_handle_cqe() >>>>> -> nvme_end_request() >>>>> -> blk_mq_complete_request() >>>>> -> __blk_mq_complete_request() >>>>> -> __blk_mq_complete_request() >>>> >>>> nvme_dev_disable will first disable the queues before reaping the pending cqes so >>>> it shouldn't have this issue. >>>> >>> >>> Would you mind help explain how nvme_dev_disable() would avoid this issue? >>> >>> nvme_dev_disable() would: >>> >>> 1. freeze all the queues so that new request would not enter and submit >>> 2. NOT wait for freezing during live reset so that q->q_usage_counter is not >>> guaranteed to be zero. >>> 3. quiesce all the queues so that new request would not dispatch >>> 4. delete the queue and free irq >>> >>> However, I do not find a mechanism to prevent if a nvme_end_request() is already >>> in progress. >>> >>> E.g., suppose __blk_mq_complete_request() is already triggered on cpu 3 and >>> waiting for its first line "WRITE_ONCE(rq->state, MQ_RQ_COMPLETE)" to be >>> executed ... while another cpu is doing live reset. I do not see how to prevent >>> such race. >> >> The queues and their interrupts are torn and synchronized down before the reset >> reclaims uncompleted requests. There's no other context that can be running >> completions at that point. > > Thank you very much for the clarification. > > There are 3 cases for a nvme request to complete. > > 1. In the context of irq. > > While I did not test with source code, I think it is because > nvme_suspend_queue()-->pci_free_irq() which would wait for all infligh IRQ > handler with __synchronize_hardirq(). > > 2. In the context of irq thread when threaded irq is involved. > > The nvme_suspend_queue()-->pci_free_irq() would finally wait for the stop of irq > thread by kthread_stop(action->thread). Therefore, there is not any IRQ handler > running in kernel thread. > > 3. In the context of blk_poll(). > > I do not find a mechanism to protect the race in this case. > > By adding mdelay() to code, I am able to reproduce the below race on purpose. > > > [ 235.223975] ================================================================== > [ 235.224878] BUG: KASAN: null-ptr-deref in blk_mq_free_request+0x363/0x510 > [ 235.225674] Write of size 4 at addr 0000000000000198 by task swapper/3/0 > [ 235.226456] > [ 235.226772] ================================================================== > [ 235.227633] BUG: kernel NULL pointer dereference, address: 0000000000000198 > [ 235.228447] #PF: supervisor write access in kernel mode > [ 235.229062] #PF: error_code(0x0002) - not-present page > [ 235.229667] PGD 0 P4D 0 > [ 235.229976] Oops: 0002 [#1] SMP KASAN PTI > [ 235.230451] CPU: 3 PID: 0 Comm: swapper/3 Tainted: G B > 5.7.0-rc5+ #1 > [ 235.231347] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 > [ 235.232692] RIP: 0010:blk_mq_free_request+0x367/0x510 > [ 235.233286] Code: 89 df 5b 5d 41 5c 41 5d 41 5e 41 5f e9 a2 dc ff ff 48 8d ba > 98 01 00 00 be 04 00 00 00 48 89 14 24 e8 fd 69 9a ff 48 8b 14 24 <f0> ff 8a 98 > 01 00 00 e9 e2 fe ff ff 48 83 c4 08 48 89 ef be 03 00 > [ 235.235503] RSP: 0018:ffff8881f7389be0 EFLAGS: 00010046 > [ 235.236114] RAX: 0000000000000000 RBX: ffff8881f21b9680 RCX: ffffffff816e05b1 > [ 235.236941] RDX: 0000000000000000 RSI: 0000000000000046 RDI: 0000000000000046 > [ 235.237770] RBP: 0000000000000001 R08: fffffbfff0af5869 R09: fffffbfff0af5869 > [ 235.238598] R10: ffffffff857ac347 R11: fffffbfff0af5868 R12: ffff8881f21b969c > [ 235.239424] R13: ffff8881f0f62738 R14: ffffe8ffffd884c0 R15: ffff8881f21b9698 > [ 235.240255] FS: 0000000000000000(0000) GS:ffff8881f7380000(0000) > knlGS:0000000000000000 > [ 235.241192] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 235.241863] CR2: 0000000000000198 CR3: 00000001eb886004 CR4: 0000000000360ee0 > [ 235.242695] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 235.243523] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 235.244349] Call Trace: > [ 235.244645] <IRQ> > [ 235.244890] blk_mq_complete_request+0x266/0x460 > [ 235.245432] nvmet_req_complete+0xd/0xb0 > [ 235.245898] iomap_dio_bio_end_io+0x336/0x480 > [ 235.246409] blk_update_request+0x320/0x960 > [ 235.246904] blk_mq_end_request+0x4e/0x4d0 > [ 235.247391] blk_mq_complete_request+0x266/0x460 > [ 235.247937] virtblk_done+0x164/0x300 > [ 235.248372] ? loop_queue_work.cold.44+0x5e/0x5e > [ 235.248915] ? rcu_accelerate_cbs+0x5d/0x1a70 > [ 235.249429] ? virtqueue_get_used_addr+0x140/0x140 > [ 235.249990] vring_interrupt+0x16d/0x280 > [ 235.250454] __handle_irq_event_percpu+0xdd/0x470 > [ 235.251010] handle_irq_event_percpu+0x6e/0x130 > [ 235.251544] ? rcu_accelerate_cbs_unlocked+0x110/0x110 > [ 235.252145] ? __handle_irq_event_percpu+0x470/0x470 > [ 235.252729] ? _raw_spin_lock+0x75/0xd0 > [ 235.253181] ? _raw_write_lock+0xd0/0xd0 > [ 235.253645] handle_irq_event+0xc2/0x158 > [ 235.254107] handle_edge_irq+0x1e9/0x7a0 > [ 235.254572] do_IRQ+0x94/0x1e0 > [ 235.254936] common_interrupt+0xf/0xf > [ 235.255368] </IRQ> > [ 235.255629] RIP: 0010:native_safe_halt+0xe/0x10 > [ 235.256162] Code: e9 f2 fe ff ff 48 89 df e8 2f dc f8 fd eb a4 cc cc cc cc cc > cc cc cc cc cc cc cc cc e9 07 00 00 00 0f 00 2d a4 7d 4a 00 fb f4 <c3> 90 e9 07 > 00 00 00 0f 00 2d 94 7d 4a 00 f4 c3 cc cc 41 56 41 55 > [ 235.258314] RSP: 0018:ffff8881f61ffdd8 EFLAGS: 00000246 ORIG_RAX: > ffffffffffffffde > [ 235.259194] RAX: ffffffff83bc59f0 RBX: dffffc0000000000 RCX: ffffffff83bc6639 > [ 235.260022] RDX: 1ffff1103ec398e8 RSI: 0000000000000008 RDI: ffff8881f61cc740 > [ 235.260850] RBP: 0000000000000003 R08: ffffed103ec398e9 R09: ffffed103ec398e9 > [ 235.261681] R10: ffff8881f61cc747 R11: ffffed103ec398e8 R12: ffffffff84e5c4c0 > [ 235.262508] R13: 0000000000000003 R14: 1ffff1103ec3ffc4 R15: 0000000000000000 > [ 235.263338] ? __cpuidle_text_start+0x8/0x8 > [ 235.263832] ? default_idle_call+0x29/0x60 > [ 235.264315] ? tsc_verify_tsc_adjust+0x68/0x1f0 > [ 235.264849] default_idle+0x1a/0x2b0 > [ 235.265273] do_idle+0x2fd/0x3b0 > [ 235.265658] ? arch_cpu_idle_exit+0x40/0x40 > [ 235.266151] ? schedule_idle+0x56/0x90 > [ 235.266595] cpu_startup_entry+0x14/0x20 > [ 235.267057] start_secondary+0x2a6/0x340 > [ 235.267522] ? set_cpu_sibling_map+0x1fb0/0x1fb0 > [ 235.268066] secondary_startup_64+0xb6/0xc0 > [ 235.268561] Modules linked in: > [ 235.268929] CR2: 0000000000000198 > [ 235.269330] ---[ end trace f8fa823705a3dbe7 ]--- > [ 235.269875] RIP: 0010:blk_mq_free_request+0x367/0x510 > [ 235.270466] Code: 89 df 5b 5d 41 5c 41 5d 41 5e 41 5f e9 a2 dc ff ff 48 8d ba > 98 01 00 00 be 04 00 00 00 48 89 14 24 e8 fd 69 9a ff 48 8b 14 24 <f0> ff 8a 98 > 01 00 00 e9 e2 fe ff ff 48 83 c4 08 48 89 ef be 03 00 > [ 235.272622] RSP: 0018:ffff8881f7389be0 EFLAGS: 00010046 > [ 235.273230] RAX: 0000000000000000 RBX: ffff8881f21b9680 RCX: ffffffff816e05b1 > [ 235.274063] RDX: 0000000000000000 RSI: 0000000000000046 RDI: 0000000000000046 > [ 235.274890] RBP: 0000000000000001 R08: fffffbfff0af5869 R09: fffffbfff0af5869 > [ 235.275717] R10: ffffffff857ac347 R11: fffffbfff0af5868 R12: ffff8881f21b969c > [ 235.276545] R13: ffff8881f0f62738 R14: ffffe8ffffd884c0 R15: ffff8881f21b9698 > [ 235.277371] FS: 0000000000000000(0000) GS:ffff8881f7380000(0000) > knlGS:0000000000000000 > [ 235.278307] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 235.278977] CR2: 0000000000000198 CR3: 00000001eb886004 CR4: 0000000000360ee0 > [ 235.279805] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 235.280632] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 235.281459] Kernel panic - not syncing: Fatal exception in interrupt > [ 235.282474] Kernel Offset: 0x400000 from 0xffffffff81000000 (relocation > range: 0xffffffff80000000-0xffffffffbfffffff) > [ 235.283695] ---[ end Kernel panic - not syncing: Fatal exception in interrupt > ]--- I copied the wrong callstack for another issue. Here is the callstack I reproduced for "nvme-pci: avoid race between nvme_reap_pending_cqes() and nvme_poll()". [ 432.997264] ------------[ cut here ]------------ [ 432.997265] refcount_t: underflow; use-after-free. [ 432.997303] WARNING: CPU: 2 PID: 836 at lib/refcount.c:28 refcount_warn_saturate+0xb0/0x150 [ 432.997304] Modules linked in: [ 432.997313] CPU: 2 PID: 836 Comm: fio Not tainted 5.7.0-rc7+ #22 [ 432.997315] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 [ 432.997320] RIP: 0010:refcount_warn_saturate+0xb0/0x150 [ 432.997323] Code: 4b 84 d9 02 01 e8 ae 8f 4d ff 0f 0b eb d0 80 3d 39 84 d9 02 00 75 c7 48 c7 c7 60 9f 75 b3 c6 05 29 84 d9 02 01 e8 8e 8f 4d ff <0f> 0b eb b0 80 3d 17 84 d9 02 00 75 a7 48 c7 c7 20 a0 75 b3 c6 05 [ 432.997324] RSP: 0018:ffff8881e18173c8 EFLAGS: 00010282 [ 432.997326] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000 [ 432.997327] RDX: 0000000000000002 RSI: 0000000000000007 RDI: ffffffffb4d70de0 [ 432.997328] RBP: ffff8881f08a63d0 R08: ffffed103ee64501 R09: ffffed103ee64501 [ 432.997330] R10: ffff8881f7322803 R11: ffffed103ee64500 R12: ffffe8ffffc00500 [ 432.997331] R13: 0000000000000000 R14: ffff8881f08a6300 R15: ffff8881f589d3c0 [ 432.997333] FS: 00007f2257ba8ec0(0000) GS:ffff8881f7300000(0000) knlGS:0000000000000000 [ 432.997334] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 432.997335] CR2: 00007ffb53b82010 CR3: 00000001f38d6001 CR4: 0000000000360ee0 [ 432.997338] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 432.997339] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 432.997340] Call Trace: [ 432.997349] blk_mq_complete_request+0x135/0x490 [ 432.997353] nvme_poll+0x49a/0xa80 [ 432.997356] blk_poll+0x5b0/0xb90 [ 432.997359] ? blk_mq_alloc_request_hctx+0x310/0x310 [ 432.997361] ? submit_bio+0x97/0x370 [ 432.997362] ? generic_make_request+0x8e0/0x8e0 [ 432.997371] ? unlock_page+0x3a/0x60 [ 432.997374] ? bio_release_pages.part.45+0x165/0x2d0 [ 432.997377] ? memset+0x1f/0x40 [ 432.997380] __blkdev_direct_IO_simple+0x515/0x7d0 [ 432.997384] ? blkdev_write_iter+0x3f0/0x3f0 [ 432.997388] ? __sched_text_start+0x8/0x8 [ 432.997390] ? __switch_to_asm+0x40/0x70 [ 432.997392] ? __switch_to_asm+0x34/0x70 [ 432.997393] ? __switch_to_asm+0x40/0x70 [ 432.997395] ? apic_timer_interrupt+0xa/0x20 [ 432.997399] ? blkdev_iopoll+0x160/0x160 [ 432.997401] ? filemap_check_errors+0x4b/0xd0 [ 432.997403] blkdev_direct_IO+0xdaf/0x1160 [ 432.997404] ? __schedule+0x815/0x16a0 [ 432.997406] ? __sched_text_start+0x8/0x8 [ 432.997410] ? deref_stack_reg+0xab/0xe0 [ 432.997411] ? blkdev_write_end+0x70/0x70 [ 432.997413] ? apic_timer_interrupt+0xa/0x20 [ 432.997414] ? apic_timer_interrupt+0xa/0x20 [ 432.997417] ? bio_release_pages.part.45+0x165/0x2d0 [ 432.997420] generic_file_read_iter+0x251/0x1b70 [ 432.997424] ? _raw_spin_unlock_irq+0x3b/0x60 [ 432.997426] ? __switch_to_asm+0x34/0x70 [ 432.997428] ? __schedule+0x815/0x16a0 [ 432.997429] ? __switch_to_asm+0x34/0x70 [ 432.997431] ? __sched_text_start+0x8/0x8 [ 432.997433] ? pagecache_get_page+0x520/0x520 [ 432.997434] ? apic_timer_interrupt+0xa/0x20 [ 432.997436] ? apic_timer_interrupt+0xa/0x20 [ 432.997437] ? apic_timer_interrupt+0xa/0x20 [ 432.997440] do_iter_readv_writev+0x485/0x6e0 [ 432.997442] ? no_seek_end_llseek_size+0x20/0x20 [ 432.997445] ? security_file_permission+0x19a/0x390 [ 432.997447] do_iter_read+0x1e5/0x590 [ 432.997450] vfs_readv+0xc7/0x130 [ 432.997451] ? __switch_to_asm+0x34/0x70 [ 432.997453] ? compat_rw_copy_check_uvector+0x300/0x300 [ 432.997455] ? __switch_to_asm+0x40/0x70 [ 432.997456] ? __switch_to_asm+0x40/0x70 [ 432.997458] ? __switch_to_asm+0x34/0x70 [ 432.997459] ? __switch_to_asm+0x40/0x70 [ 432.997461] ? __switch_to_asm+0x34/0x70 [ 432.997462] ? __switch_to_asm+0x40/0x70 [ 432.997464] ? _raw_spin_unlock_irq+0x3b/0x60 [ 432.997466] ? apic_timer_interrupt+0xa/0x20 [ 432.997467] ? apic_timer_interrupt+0xa/0x20 [ 432.997470] do_preadv+0x14c/0x1f0 [ 432.997472] ? __ia32_sys_readv+0xa0/0xa0 [ 432.997475] do_syscall_64+0x91/0x330 [ 432.997477] ? prepare_exit_to_usermode+0xfc/0x1d0 [ 432.997479] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 432.997486] RIP: 0033:0x7f2255a55950 [ 432.997488] Code: 66 2e 0f 1f 84 00 00 00 00 00 e8 ab 9d 01 00 41 89 d9 41 89 c7 45 31 c0 4d 89 f2 44 89 ea 4c 89 e6 89 ef b8 47 01 00 00 0f 05 <48> 3d 00 f0 ff ff 77 32 44 89 ff 48 89 44 24 08 e8 db 9d 01 00 48 [ 432.997489] RSP: 002b:00007ffd0051ce10 EFLAGS: 00000246 ORIG_RAX: 0000000000000147 [ 432.997491] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f2255a55950 [ 432.997492] RDX: 0000000000000001 RSI: 000055e73f7f78b0 RDI: 0000000000000003 [ 432.997493] RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000001 [ 432.997494] R10: 0000000043ac2000 R11: 0000000000000246 R12: 000055e73f7f78b0 [ 432.997494] R13: 0000000000000001 R14: 0000000043ac2000 R15: 0000000000000000 [ 432.997497] ---[ end trace 276357d6d1512fac ]--- Dongli Zhang > > > > I have sent the below for feedback. > > https://lore.kernel.org/linux-nvme/20200527004955.19463-1-dongli.zhang@xxxxxxxxxx/T/#u > > Thank you very much! > > Dongli Zhang >
