[PATCH] RDMA/erdma: Fix CEQ tasklet use-after-free on removal

[Myeonghun Pak]

Each CEQ interrupt handler only schedules eqc->tasklet. The tasklet calls
erdma_ceq_completion_handler(), which reads the DMA-coherent EQ ring
through get_next_valid_eqe() and updates eq->dbrec through notify_eq().

erdma_ceqs_uninit() frees each CEQ IRQ and then destroys its EQ.
free_irq() prevents another hard IRQ and waits for an in-flight handler,
but it does not drain a tasklet that the handler already scheduled. The
tasklet can therefore access eq->qbuf or eq->dbrec after
erdma_eq_destroy() frees them.

Clearing ceq_cb->ready does not synchronize with a tasklet that already
passed the check at the start of erdma_ceq_completion_handler().

Kill the tasklet after free_irq(), when no handler can schedule it again,
and before erdma_ceq_uninit_one() releases the EQ buffers.

Fixes: f2a0a630b953 ("RDMA/erdma: Add event queue implementation")
Cc: stable@xxxxxxxxxxxxxxx
Co-developed-by: Ijae Kim <ae878000@xxxxxxxxx>
Signed-off-by: Ijae Kim <ae878000@xxxxxxxxx>
Signed-off-by: Myeonghun Pak <mhun512@xxxxxxxxx>
---
Found by static analysis only; not tested on ERDMA hardware. Testing on
hardware, particularly device removal while CEQ interrupts are active,
would be appreciated.

 drivers/infiniband/hw/erdma/erdma_eq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/infiniband/hw/erdma/erdma_eq.c b/drivers/infiniband/hw/erdma/erdma_eq.c
index d5b9d19882b2..a8784e07acd6 100644
--- a/drivers/infiniband/hw/erdma/erdma_eq.c
+++ b/drivers/infiniband/hw/erdma/erdma_eq.c
@@ -220,6 +220,7 @@ static void erdma_free_ceq_irq(struct erdma_dev *dev, u16 ceqn)
 
 	irq_set_affinity_hint(eqc->irq.msix_vector, NULL);
 	free_irq(eqc->irq.msix_vector, eqc);
+	tasklet_kill(&eqc->tasklet);
 }
 
 static int create_eq_cmd(struct erdma_dev *dev, u32 eqn, struct erdma_eq *eq)
-- 
2.47.1