On Wed, Apr 20, 2016 at 04:44:27PM +0200, Lukas Wunner wrote:
> Previously when pci_bus_add_device() called device_attach() and it
> returned a negative value, we emitted a WARN but carried on.
>
> Commit ab1a187bba5c ("PCI: Check device_attach() return value always"),
> introduced in Linux 4.6-rc1, changed this to unwind all steps preceding
> device_attach() and to not set dev->is_added = 1.
>
> The latter leads to a BUG if pci_bus_add_device() was called from
> pci_bus_add_devices(). Fix by not recursing to a child bus if
> device_attach() failed for the bridge leading to it.
>
> This can be triggered by plugging in a PCI device (e.g. Thunderbolt)
> while the system is asleep. The system locks up when woken because
> device_attach() returns -EPROBE_DEFER.
>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Applied both with Rafael's acks to for-linus for v4.6.
The rationale is that ab1a187bba5c ("PCI: Check device_attach() return
value always") appeared in v4.6-rc1, and after that commit, plugging
in a Thunderbolt device while the system is asleep will cause a BUG()
when the system is awakened.
Lukas, you mentioned earlier that we might want to include Andreas'
patch "thunderbolt: Fix double free of drom buffer" at the same time.
I did apply that on pci/thunderbolt for v4.7. I can move that to
for-linus and put it in v4.6 if necessary, but that bug been there
since v3.17. Is there something in v4.6 that makes us more likely to
hit that double free?
> ---
> v2: Split commit in two (Bjorn Helgaas).
>
> drivers/pci/bus.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 6c9f546..23a39fd 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -324,7 +324,9 @@ void pci_bus_add_devices(const struct pci_bus *bus)
> }
>
> list_for_each_entry(dev, &bus->devices, bus_list) {
> - BUG_ON(!dev->is_added);
> + /* Skip if device attach failed */
> + if (!dev->is_added)
> + continue;
> child = dev->subordinate;
> if (child)
> pci_bus_add_devices(child);
> --
> 2.8.0.rc3
>
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