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| author | Bjorn Helgaas <bhelgaas@google.com> | 2020-06-26 02:14:55 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-08-21 12:02:01 +0300 |
| commit | f5808a905d4ec1853463e411bc1688314e8bc313 (patch) | |
| tree | 44034972c17dc9a8be8e714330a03e3c90776324 | |
| parent | c41bc070d236bfaa8217b983f7ccdf58f8bdccf0 (diff) | |
| download | linux-f5808a905d4ec1853463e411bc1688314e8bc313.tar.xz | |
PCI: Fix pci_cfg_wait queue locking problem
[ Upstream commit 2a7e32d0547f41c5ce244f84cf5d6ca7fccee7eb ]
The pci_cfg_wait queue is used to prevent user-space config accesses to
devices while they are recovering from reset.
Previously we used these operations on pci_cfg_wait:
__add_wait_queue(&pci_cfg_wait, ...)
__remove_wait_queue(&pci_cfg_wait, ...)
wake_up_all(&pci_cfg_wait)
The wake_up acquires the wait queue lock, but the add and remove do not.
Originally these were all protected by the pci_lock, but cdcb33f98244
("PCI: Avoid possible deadlock on pci_lock and p->pi_lock"), moved
wake_up_all() outside pci_lock, so it could race with add/remove
operations, which caused occasional kernel panics, e.g., during vfio-pci
hotplug/unplug testing:
Unable to handle kernel read from unreadable memory at virtual address ffff802dac469000
Resolve this by using wait_event() instead of __add_wait_queue() and
__remove_wait_queue(). The wait queue lock is held by both wait_event()
and wake_up_all(), so it provides mutual exclusion.
Fixes: cdcb33f98244 ("PCI: Avoid possible deadlock on pci_lock and p->pi_lock")
Link: https://lore.kernel.org/linux-pci/79827f2f-9b43-4411-1376-b9063b67aee3@huawei.com/T/#u
Based-on: https://lore.kernel.org/linux-pci/20191210031527.40136-1-zhengxiang9@huawei.com/
Based-on-patch-by: Xiang Zheng <zhengxiang9@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Xiang Zheng <zhengxiang9@huawei.com>
Cc: Heyi Guo <guoheyi@huawei.com>
Cc: Biaoxiang Ye <yebiaoxiang@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/pci/access.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/drivers/pci/access.c b/drivers/pci/access.c index 7b5cf6d1181a..6f2a07567532 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -185,17 +185,13 @@ EXPORT_SYMBOL(pci_bus_set_ops); static DECLARE_WAIT_QUEUE_HEAD(pci_cfg_wait); static noinline void pci_wait_cfg(struct pci_dev *dev) + __must_hold(&pci_lock) { - DECLARE_WAITQUEUE(wait, current); - - __add_wait_queue(&pci_cfg_wait, &wait); do { - set_current_state(TASK_UNINTERRUPTIBLE); raw_spin_unlock_irq(&pci_lock); - schedule(); + wait_event(pci_cfg_wait, !dev->block_cfg_access); raw_spin_lock_irq(&pci_lock); } while (dev->block_cfg_access); - __remove_wait_queue(&pci_cfg_wait, &wait); } /* Returns 0 on success, negative values indicate error. */ |