3.19.8-ckt16 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
commit 4ae2182b1e3407de369f8c5d799543b7db74221b upstream.
A Root Port's AER structure (rpc) contains a queue of events. aer_irq()
enqueues AER status information and schedules aer_isr() to dequeue and
process it. When we remove a device, aer_remove() waits for the queue to
be empty, then frees the rpc struct.
But aer_isr() references the rpc struct after dequeueing and possibly
emptying the queue, which can cause a use-after-free error as in the
following scenario with two threads, aer_isr() on the left and a
concurrent aer_remove() on the right:
Thread A Thread B
-------- --------
aer_irq():
rpc->prod_idx++
aer_remove():
wait_event(rpc->prod_idx == rpc->cons_idx)
# now blocked until queue becomes empty
aer_isr(): # ...
rpc->cons_idx++ # unblocked because queue is now empty
... kfree(rpc)
mutex_unlock(&rpc->rpc_mutex)
To prevent this problem, use flush_work() to wait until the last scheduled
instance of aer_isr() has completed before freeing the rpc struct in
aer_remove().
I reproduced this use-after-free by flashing a device FPGA and
re-enumerating the bus to find the new device. With SLUB debug, this
crashes with 0x6b bytes (POISON_FREE, the use-after-free magic number) in
GPR25:
pcieport 0000:00:00.0: AER: Multiple Corrected error received: id=0000
Unable to handle kernel paging request for data at address 0x27ef9e3e
Workqueue: events aer_isr
GPR24: dd6aa000 6b6b6b6b 605f8378 605f8360 d99b12c0 604fc674 606b1704 d99b12c0
NIP [602f5328] pci_walk_bus+0xd4/0x104
[bhelgaas: changelog, stable tag]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
drivers/pci/pcie/aer/aerdrv.c | 4 +---
drivers/pci/pcie/aer/aerdrv.h | 1 -
drivers/pci/pcie/aer/aerdrv_core.c | 2 --
3 files changed, 1 insertion(+), 6 deletions(-)
diff --git a/drivers/pci/pcie/aer/aerdrv.c b/drivers/pci/pcie/aer/aerdrv.c
index 0bf82a2..48d21e0 100644
--- a/drivers/pci/pcie/aer/aerdrv.c
+++ b/drivers/pci/pcie/aer/aerdrv.c
@@ -262,7 +262,6 @@ static struct aer_rpc *aer_alloc_rpc(struct pcie_device *dev)
rpc->rpd = dev;
INIT_WORK(&rpc->dpc_handler, aer_isr);
mutex_init(&rpc->rpc_mutex);
- init_waitqueue_head(&rpc->wait_release);
/* Use PCIe bus function to store rpc into PCIe device */
set_service_data(dev, rpc);
@@ -285,8 +284,7 @@ static void aer_remove(struct pcie_device *dev)
if (rpc->isr)
free_irq(dev->irq, dev);
- wait_event(rpc->wait_release, rpc->prod_idx == rpc->cons_idx);
-
+ flush_work(&rpc->dpc_handler);
aer_disable_rootport(rpc);
kfree(rpc);
set_service_data(dev, NULL);
diff --git a/drivers/pci/pcie/aer/aerdrv.h b/drivers/pci/pcie/aer/aerdrv.h
index 84420b7..945c939 100644
--- a/drivers/pci/pcie/aer/aerdrv.h
+++ b/drivers/pci/pcie/aer/aerdrv.h
@@ -72,7 +72,6 @@ struct aer_rpc {
* recovery on the same
* root port hierarchy
*/
- wait_queue_head_t wait_release;
};
struct aer_broadcast_data {
diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index 5653ea9..b60a325 100644
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -784,8 +784,6 @@ void aer_isr(struct work_struct *work)
while (get_e_source(rpc, &e_src))
aer_isr_one_error(p_device, &e_src);
mutex_unlock(&rpc->rpc_mutex);
-
- wake_up(&rpc->wait_release);
}
/**
--
2.7.0
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