[PATCH] Fix race bug in nvme_poll_irqdisable()

[Sungwoo Kim]

In the following scenario, pdev can be disabled between (1) and (3) by
(2). This sets pdev->msix_enabled = 0. Then, pci_irq_vector() will
return MSI-X IRQ(>15) for (1) whereas return INTx IRQ(<=15) for (2).
This causes IRQ warning because it tries to enable INTx IRQ that has
never been disabled before.

To fix this, save IRQ number into a local variable and ensure
disable_irq() and enable_irq() operate on the same IRQ number.
Even if pci_free_irq_vectors() frees the IRQ concurrently, disable_irq()
and enable_irq() on a stale IRQ number is still valid and safe, and the
depth accounting reamins balanced.

task 1:
nvme_poll_irqdisable()
  disable_irq(pci_irq_vector(pdev, nvmeq->cq_vector)) ...(1)
  enable_irq(pci_irq_vector(pdev, nvmeq->cq_vector))  ...(3)

task 2:
nvme_reset_work()
  nvme_dev_disable()
    pdev->msix_enable = 0;  ...(2)

crash log:

------------[ cut here ]------------
Unbalanced enable for IRQ 10
WARNING: kernel/irq/manage.c:753 at __enable_irq+0x102/0x190 kernel/irq/manage.c:753, CPU#1: kworker/1:0H/26
Modules linked in:
CPU: 1 UID: 0 PID: 26 Comm: kworker/1:0H Not tainted 6.19.0-dirty #9 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
Workqueue: kblockd blk_mq_timeout_work
RIP: 0010:__enable_irq+0x107/0x190 kernel/irq/manage.c:753
Code: ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 79 48 8d 3d 2e 7a 3f 05 41 8b 74 24 2c <67> 48 0f b9 3a e8 ef b9 21 00 5b 41 5c 5d e9 46 54 66 03 e8 e1 b9
RSP: 0018:ffffc900001bf550 EFLAGS: 00010046
RAX: 0000000000000007 RBX: 0000000000000000 RCX: ffffffffb20c0e90
RDX: 0000000000000000 RSI: 000000000000000a RDI: ffffffffb74b88f0
RBP: ffffc900001bf560 R08: ffff88800197cf00 R09: 0000000000000001
R10: 0000000000000003 R11: 0000000000000003 R12: ffff8880012a6000
R13: 1ffff92000037eae R14: 000000000000000a R15: 0000000000000293
FS:  0000000000000000(0000) GS:ffff8880b49f7000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555da4a25fa8 CR3: 00000000208e8000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 enable_irq+0x121/0x1e0 kernel/irq/manage.c:797
 nvme_poll_irqdisable+0x162/0x1c0 drivers/nvme/host/pci.c:1494
 nvme_timeout+0x965/0x14b0 drivers/nvme/host/pci.c:1744
 blk_mq_rq_timed_out block/blk-mq.c:1653 [inline]
 blk_mq_handle_expired+0x227/0x2d0 block/blk-mq.c:1721
 bt_iter+0x2fc/0x3a0 block/blk-mq-tag.c:292
 __sbitmap_for_each_set include/linux/sbitmap.h:269 [inline]
 sbitmap_for_each_set include/linux/sbitmap.h:290 [inline]
 bt_for_each block/blk-mq-tag.c:324 [inline]
 blk_mq_queue_tag_busy_iter+0x969/0x1e80 block/blk-mq-tag.c:536
 blk_mq_timeout_work+0x627/0x870 block/blk-mq.c:1763
 process_one_work+0x956/0x1aa0 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x65c/0xe60 kernel/workqueue.c:3421
 kthread+0x41a/0x930 kernel/kthread.c:463
 ret_from_fork+0x6f8/0x8c0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
irq event stamp: 74478
hardirqs last  enabled at (74477): [<ffffffffb5720a9c>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:159 [inline]
hardirqs last  enabled at (74477): [<ffffffffb5720a9c>] _raw_spin_unlock_irq+0x2c/0x60 kernel/locking/spinlock.c:202
hardirqs last disabled at (74478): [<ffffffffb57207b5>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
hardirqs last disabled at (74478): [<ffffffffb57207b5>] _raw_spin_lock_irqsave+0x85/0xa0 kernel/locking/spinlock.c:162
softirqs last  enabled at (74304): [<ffffffffb1e9466c>] __do_softirq kernel/softirq.c:656 [inline]
softirqs last  enabled at (74304): [<ffffffffb1e9466c>] invoke_softirq kernel/softirq.c:496 [inline]
softirqs last  enabled at (74304): [<ffffffffb1e9466c>] __irq_exit_rcu+0xdc/0x120 kernel/softirq.c:723
softirqs last disabled at (74287): [<ffffffffb1e9466c>] __do_softirq kernel/softirq.c:656 [inline]
softirqs last disabled at (74287): [<ffffffffb1e9466c>] invoke_softirq kernel/softirq.c:496 [inline]
softirqs last disabled at (74287): [<ffffffffb1e9466c>] __irq_exit_rcu+0xdc/0x120 kernel/softirq.c:723
---[ end trace 0000000000000000 ]---

Fixes: fa059b856a59 (nvme-pci: Simplify nvme_poll_irqdisable)
Acked-by: Chao Shi <cshi008 at fiu.edu>
Acked-by: Weidong Zhu <weizhu at fiu.edu>
Acked-by: Dave Tian <daveti at purdue.edu>
Signed-off-by: Sungwoo Kim <iam at sung-woo.kim>
---
 drivers/nvme/host/pci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index d86f2565a..a7fb88aa8 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1484,14 +1484,16 @@ static irqreturn_t nvme_irq_check(int irq, void *data)
 static void nvme_poll_irqdisable(struct nvme_queue *nvmeq)
 {
 	struct pci_dev *pdev = to_pci_dev(nvmeq->dev->dev);
+	int irq;
 
 	WARN_ON_ONCE(test_bit(NVMEQ_POLLED, &nvmeq->flags));
 
-	disable_irq(pci_irq_vector(pdev, nvmeq->cq_vector));
+	irq = pci_irq_vector(pdev, nvmeq->cq_vector);
+	disable_irq(irq);
 	spin_lock(&nvmeq->cq_poll_lock);
 	nvme_poll_cq(nvmeq, NULL);
 	spin_unlock(&nvmeq->cq_poll_lock);
-	enable_irq(pci_irq_vector(pdev, nvmeq->cq_vector));
+	enable_irq(irq);
 }
 
 static int nvme_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
-- 
2.47.3