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    Subject[PATCH 5.14 046/151] PCI: hv: Fix sleep while in non-sleep context when removing child devices from the bus
    Date
    From: Long Li <longli@microsoft.com>

    [ Upstream commit 41608b64b10b80fe00dd253cd8326ec8ad85930f ]

    In hv_pci_bus_exit, the code is holding a spinlock while calling
    pci_destroy_slot(), which takes a mutex.

    This is not safe for spinlock. Fix this by moving the children to be
    deleted to a list on the stack, and removing them after spinlock is
    released.

    Fixes: 94d22763207a ("PCI: hv: Fix a race condition when removing the device")

    Cc: "K. Y. Srinivasan" <kys@microsoft.com>
    Cc: Haiyang Zhang <haiyangz@microsoft.com>
    Cc: Stephen Hemminger <sthemmin@microsoft.com>
    Cc: Wei Liu <wei.liu@kernel.org>
    Cc: Dexuan Cui <decui@microsoft.com>
    Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    Cc: Rob Herring <robh@kernel.org>
    Cc: "Krzysztof Wilczyński" <kw@linux.com>
    Cc: Bjorn Helgaas <bhelgaas@google.com>
    Cc: Michael Kelley <mikelley@microsoft.com>
    Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
    Link: https://lore.kernel.org/linux-hyperv/20210823152130.GA21501@kili/
    Signed-off-by: Long Li <longli@microsoft.com>
    Reviewed-by: Wei Liu <wei.liu@kernel.org>
    Link: https://lore.kernel.org/r/1630365207-20616-1-git-send-email-longli@linuxonhyperv.com
    Signed-off-by: Wei Liu <wei.liu@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/pci/controller/pci-hyperv.c | 13 ++++++++++---
    1 file changed, 10 insertions(+), 3 deletions(-)

    diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
    index a53bd8728d0d..fc1a29acadbb 100644
    --- a/drivers/pci/controller/pci-hyperv.c
    +++ b/drivers/pci/controller/pci-hyperv.c
    @@ -3229,9 +3229,17 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
    return 0;

    if (!keep_devs) {
    - /* Delete any children which might still exist. */
    + struct list_head removed;
    +
    + /* Move all present children to the list on stack */
    + INIT_LIST_HEAD(&removed);
    spin_lock_irqsave(&hbus->device_list_lock, flags);
    - list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry) {
    + list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry)
    + list_move_tail(&hpdev->list_entry, &removed);
    + spin_unlock_irqrestore(&hbus->device_list_lock, flags);
    +
    + /* Remove all children in the list */
    + list_for_each_entry_safe(hpdev, tmp, &removed, list_entry) {
    list_del(&hpdev->list_entry);
    if (hpdev->pci_slot)
    pci_destroy_slot(hpdev->pci_slot);
    @@ -3239,7 +3247,6 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
    put_pcichild(hpdev);
    put_pcichild(hpdev);
    }
    - spin_unlock_irqrestore(&hbus->device_list_lock, flags);
    }

    ret = hv_send_resources_released(hdev);
    --
    2.33.0


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