[PATCH v3] PCI: switchtec: Fix use-after-free in switchtec_pci_remove due to race condition

In stdev_create, &stdev->mrpc_work is bound with mrpc_event_work, and
&stdev->link_event_work is bound with link_event_work. The IRQ handlers
switchtec_event_isr and switchtec_dma_mrpc_isr can schedule these works
on system_wq (via schedule_work() in the ISRs and via
check_link_state_events()).

If we remove the device, switchtec_pci_remove makes cleanup and the
memory allocated for stdev is released by put_device() ->
stdev_release() -> kfree(stdev), while the works mentioned above may
still be pending or running. The sequence of operations that may lead
to a UAF bug is as follows:

CPU0                                      CPU1

                                          | switchtec_event_isr
                                          | schedule_work(&stdev->mrpc_work)
switchtec_pci_remove                      |
cdev_device_del(&stdev->cdev,             |
                &stdev->dev)              |
stdev_kill(stdev)                         |
switchtec_exit_pci(stdev)                 |
pci_dev_put(stdev->pdev)                  |
put_device(&stdev->dev)                   |
// stdev_release -> kfree(stdev)          |
                                          | mrpc_event_work
                                          | // use stdev (use-after-free)

Fix it by quiescing the interrupt sources before canceling the works:
stdev_kill() first clears PCI bus mastering, then explicitly frees both
IRQs, so no handler can be running and scheduling new work while the works
are canceled.

Fixes: 080b47def5e5 ("MicroSemi Switchtec management interface driver")
Fixes: 48c302dc8f3a ("NTB: switchtec: Add link event notifier callback")
Cc: [email protected]
Assisted-by: Codex:deepseek-v4-flash
Reviewed-by: Logan Gunthorpe <[email protected]>
Signed-off-by: Pei Xiao <[email protected]>
---
changes in v3:
1.Add Reviewed-by: Logan Gunthorpe <[email protected]>
2.event_irq and dma_mrpc_irq explictily initialized to zero and check for non-zero in the tests
v2 Links: https://lore.kernel.org/lkml/[email protected]/#t  

changes in v2:
1.Add explicitly devm_free_irq
2.cacel mrpc_work and link_event_work move to before mrpc_timeout
3.Add event_irq and dma_mrpc_irq in struct stdev
4.Add Cc: [email protected]
---
 drivers/pci/switch/switchtec.c | 16 +++++++++++++++-
 include/linux/switchtec.h      |  2 ++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
index 5711aaa5df11..9eded14a37b1 100644
--- a/drivers/pci/switch/switchtec.c
+++ b/drivers/pci/switch/switchtec.c
@@ -1318,6 +1318,13 @@ static void stdev_kill(struct switchtec_dev *stdev)
 
 	pci_clear_master(stdev->pdev);
 
+	if (stdev->event_irq)
+		devm_free_irq(&stdev->pdev->dev, stdev->event_irq, stdev);
+	if (stdev->dma_mrpc_irq)
+		devm_free_irq(&stdev->pdev->dev, stdev->dma_mrpc_irq, stdev);
+
+	cancel_work_sync(&stdev->mrpc_work);
+	cancel_work_sync(&stdev->link_event_work);
 	cancel_delayed_work_sync(&stdev->mrpc_timeout);
 
 	/* Mark the hardware as unavailable and complete all completions */
@@ -1356,6 +1363,8 @@ static struct switchtec_dev *stdev_create(struct pci_dev *pdev)
 	INIT_LIST_HEAD(&stdev->mrpc_queue);
 	mutex_init(&stdev->mrpc_mutex);
 	stdev->mrpc_busy = 0;
+	stdev->event_irq = 0;
+	stdev->dma_mrpc_irq = 0;
 	INIT_WORK(&stdev->mrpc_work, mrpc_event_work);
 	INIT_DELAYED_WORK(&stdev->mrpc_timeout, mrpc_timeout_work);
 	INIT_WORK(&stdev->link_event_work, link_event_work);
@@ -1513,6 +1522,7 @@ static int switchtec_init_isr(struct switchtec_dev *stdev)
 
 	if (rc)
 		return rc;
+	stdev->event_irq = event_irq;
 
 	if (!stdev->dma_mrpc)
 		return rc;
@@ -1529,7 +1539,11 @@ static int switchtec_init_isr(struct switchtec_dev *stdev)
 				switchtec_dma_mrpc_isr, 0,
 				KBUILD_MODNAME, stdev);
 
-	return rc;
+	if (rc)
+		return rc;
+	stdev->dma_mrpc_irq = dma_mrpc_irq;
+
+	return 0;
 }
 
 static void init_pff(struct switchtec_dev *stdev)
diff --git a/include/linux/switchtec.h b/include/linux/switchtec.h
index 724da6c08bf7..fd38d3e7f3b6 100644
--- a/include/linux/switchtec.h
+++ b/include/linux/switchtec.h
@@ -500,6 +500,8 @@ struct switchtec_dev {
 	struct mutex mrpc_mutex;
 	struct list_head mrpc_queue;
 	int mrpc_busy;
+	int event_irq;
+	int dma_mrpc_irq;
 	struct work_struct mrpc_work;
 	struct delayed_work mrpc_timeout;
 	bool alive;
-- 
2.25.1