| From fa765c4b4aed2d64266b694520ecb025c862c5a9 Mon Sep 17 00:00:00 2001 |
| From: Maximilian Heyne <mheyne@amazon.de> |
| Date: Wed, 24 Jan 2024 16:31:28 +0000 |
| Subject: xen/events: close evtchn after mapping cleanup |
| |
| From: Maximilian Heyne <mheyne@amazon.de> |
| |
| commit fa765c4b4aed2d64266b694520ecb025c862c5a9 upstream. |
| |
| shutdown_pirq and startup_pirq are not taking the |
| irq_mapping_update_lock because they can't due to lock inversion. Both |
| are called with the irq_desc->lock being taking. The lock order, |
| however, is first irq_mapping_update_lock and then irq_desc->lock. |
| |
| This opens multiple races: |
| - shutdown_pirq can be interrupted by a function that allocates an event |
| channel: |
| |
| CPU0 CPU1 |
| shutdown_pirq { |
| xen_evtchn_close(e) |
| __startup_pirq { |
| EVTCHNOP_bind_pirq |
| -> returns just freed evtchn e |
| set_evtchn_to_irq(e, irq) |
| } |
| xen_irq_info_cleanup() { |
| set_evtchn_to_irq(e, -1) |
| } |
| } |
| |
| Assume here event channel e refers here to the same event channel |
| number. |
| After this race the evtchn_to_irq mapping for e is invalid (-1). |
| |
| - __startup_pirq races with __unbind_from_irq in a similar way. Because |
| __startup_pirq doesn't take irq_mapping_update_lock it can grab the |
| evtchn that __unbind_from_irq is currently freeing and cleaning up. In |
| this case even though the event channel is allocated, its mapping can |
| be unset in evtchn_to_irq. |
| |
| The fix is to first cleanup the mappings and then close the event |
| channel. In this way, when an event channel gets allocated it's |
| potential previous evtchn_to_irq mappings are guaranteed to be unset already. |
| This is also the reverse order of the allocation where first the event |
| channel is allocated and then the mappings are setup. |
| |
| On a 5.10 kernel prior to commit 3fcdaf3d7634 ("xen/events: modify internal |
| [un]bind interfaces"), we hit a BUG like the following during probing of NVMe |
| devices. The issue is that during nvme_setup_io_queues, pci_free_irq |
| is called for every device which results in a call to shutdown_pirq. |
| With many nvme devices it's therefore likely to hit this race during |
| boot because there will be multiple calls to shutdown_pirq and |
| startup_pirq are running potentially in parallel. |
| |
| ------------[ cut here ]------------ |
| blkfront: xvda: barrier or flush: disabled; persistent grants: enabled; indirect descriptors: enabled; bounce buffer: enabled |
| kernel BUG at drivers/xen/events/events_base.c:499! |
| invalid opcode: 0000 [#1] SMP PTI |
| CPU: 44 PID: 375 Comm: kworker/u257:23 Not tainted 5.10.201-191.748.amzn2.x86_64 #1 |
| Hardware name: Xen HVM domU, BIOS 4.11.amazon 08/24/2006 |
| Workqueue: nvme-reset-wq nvme_reset_work |
| RIP: 0010:bind_evtchn_to_cpu+0xdf/0xf0 |
| Code: 5d 41 5e c3 cc cc cc cc 44 89 f7 e8 2b 55 ad ff 49 89 c5 48 85 c0 0f 84 64 ff ff ff 4c 8b 68 30 41 83 fe ff 0f 85 60 ff ff ff <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 0f 1f 44 00 00 |
| RSP: 0000:ffffc9000d533b08 EFLAGS: 00010046 |
| RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000006 |
| RDX: 0000000000000028 RSI: 00000000ffffffff RDI: 00000000ffffffff |
| RBP: ffff888107419680 R08: 0000000000000000 R09: ffffffff82d72b00 |
| R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000001ed |
| R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000002 |
| FS: 0000000000000000(0000) GS:ffff88bc8b500000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 0000000000000000 CR3: 0000000002610001 CR4: 00000000001706e0 |
| DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 |
| DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 |
| Call Trace: |
| ? show_trace_log_lvl+0x1c1/0x2d9 |
| ? show_trace_log_lvl+0x1c1/0x2d9 |
| ? set_affinity_irq+0xdc/0x1c0 |
| ? __die_body.cold+0x8/0xd |
| ? die+0x2b/0x50 |
| ? do_trap+0x90/0x110 |
| ? bind_evtchn_to_cpu+0xdf/0xf0 |
| ? do_error_trap+0x65/0x80 |
| ? bind_evtchn_to_cpu+0xdf/0xf0 |
| ? exc_invalid_op+0x4e/0x70 |
| ? bind_evtchn_to_cpu+0xdf/0xf0 |
| ? asm_exc_invalid_op+0x12/0x20 |
| ? bind_evtchn_to_cpu+0xdf/0xf0 |
| ? bind_evtchn_to_cpu+0xc5/0xf0 |
| set_affinity_irq+0xdc/0x1c0 |
| irq_do_set_affinity+0x1d7/0x1f0 |
| irq_setup_affinity+0xd6/0x1a0 |
| irq_startup+0x8a/0xf0 |
| __setup_irq+0x639/0x6d0 |
| ? nvme_suspend+0x150/0x150 |
| request_threaded_irq+0x10c/0x180 |
| ? nvme_suspend+0x150/0x150 |
| pci_request_irq+0xa8/0xf0 |
| ? __blk_mq_free_request+0x74/0xa0 |
| queue_request_irq+0x6f/0x80 |
| nvme_create_queue+0x1af/0x200 |
| nvme_create_io_queues+0xbd/0xf0 |
| nvme_setup_io_queues+0x246/0x320 |
| ? nvme_irq_check+0x30/0x30 |
| nvme_reset_work+0x1c8/0x400 |
| process_one_work+0x1b0/0x350 |
| worker_thread+0x49/0x310 |
| ? process_one_work+0x350/0x350 |
| kthread+0x11b/0x140 |
| ? __kthread_bind_mask+0x60/0x60 |
| ret_from_fork+0x22/0x30 |
| Modules linked in: |
| ---[ end trace a11715de1eee1873 ]--- |
| |
| Fixes: d46a78b05c0e ("xen: implement pirq type event channels") |
| Cc: stable@vger.kernel.org |
| Co-debugged-by: Andrew Panyakin <apanyaki@amazon.com> |
| Signed-off-by: Maximilian Heyne <mheyne@amazon.de> |
| Reviewed-by: Juergen Gross <jgross@suse.com> |
| Link: https://lore.kernel.org/r/20240124163130.31324-1-mheyne@amazon.de |
| Signed-off-by: Juergen Gross <jgross@suse.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/xen/events/events_base.c | 8 ++++++-- |
| 1 file changed, 6 insertions(+), 2 deletions(-) |
| |
| --- a/drivers/xen/events/events_base.c |
| +++ b/drivers/xen/events/events_base.c |
| @@ -923,8 +923,8 @@ static void shutdown_pirq(struct irq_dat |
| return; |
| |
| do_mask(info, EVT_MASK_REASON_EXPLICIT); |
| - xen_evtchn_close(evtchn); |
| xen_irq_info_cleanup(info); |
| + xen_evtchn_close(evtchn); |
| } |
| |
| static void enable_pirq(struct irq_data *data) |
| @@ -956,6 +956,7 @@ EXPORT_SYMBOL_GPL(xen_irq_from_gsi); |
| static void __unbind_from_irq(struct irq_info *info, unsigned int irq) |
| { |
| evtchn_port_t evtchn; |
| + bool close_evtchn = false; |
| |
| if (!info) { |
| xen_irq_free_desc(irq); |
| @@ -975,7 +976,7 @@ static void __unbind_from_irq(struct irq |
| struct xenbus_device *dev; |
| |
| if (!info->is_static) |
| - xen_evtchn_close(evtchn); |
| + close_evtchn = true; |
| |
| switch (info->type) { |
| case IRQT_VIRQ: |
| @@ -995,6 +996,9 @@ static void __unbind_from_irq(struct irq |
| } |
| |
| xen_irq_info_cleanup(info); |
| + |
| + if (close_evtchn) |
| + xen_evtchn_close(evtchn); |
| } |
| |
| xen_free_irq(info); |
