diff options
| author | Daniel Stodden <daniel.stodden@gmail.com> | 2024-12-22 19:39:08 -0800 |
|---|---|---|
| committer | Krzysztof Wilczyński <kwilczynski@kernel.org> | 2025-02-20 10:05:56 +0000 |
| commit | cbf937dcadfd571a434f8074d057b32cd14fbea5 (patch) | |
| tree | c81d0121909c0b48a9e43e933a6b417ae3a46915 | |
| parent | 2014c95afecee3e76ca4a56956a936e23283f05b (diff) | |
PCI/ASPM: Fix link state exit during switch upstream function removal
Before 456d8aa37d0f ("PCI/ASPM: Disable ASPM on MFD function removal to
avoid use-after-free"), we would free the ASPM link only after the last
function on the bus pertaining to the given link was removed.
That was too late. If function 0 is removed before sibling function,
link->downstream would point to free'd memory after.
After above change, we freed the ASPM parent link state upon any function
removal on the bus pertaining to a given link.
That is too early. If the link is to a PCIe switch with MFD on the upstream
port, then removing functions other than 0 first would free a link which
still remains parent_link to the remaining downstream ports.
The resulting GPFs are especially frequent during hot-unplug, because
pciehp removes devices on the link bus in reverse order.
On that switch, function 0 is the virtual P2P bridge to the internal bus.
Free exactly when function 0 is removed -- before the parent link is
obsolete, but after all subordinate links are gone.
Link: https://lore.kernel.org/r/e12898835f25234561c9d7de4435590d957b85d9.1734924854.git.dns@arista.com
Fixes: 456d8aa37d0f ("PCI/ASPM: Disable ASPM on MFD function removal to avoid use-after-free")
Signed-off-by: Daniel Stodden <dns@arista.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
| -rw-r--r-- | drivers/pci/pcie/aspm.c | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index e0bc90597dca..25954cc89bf3 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -1273,16 +1273,16 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev) parent_link = link->parent; /* - * link->downstream is a pointer to the pci_dev of function 0. If - * we remove that function, the pci_dev is about to be deallocated, - * so we can't use link->downstream again. Free the link state to - * avoid this. + * Free the parent link state, no later than function 0 (i.e. + * link->downstream) being removed. * - * If we're removing a non-0 function, it's possible we could - * retain the link state, but PCIe r6.0, sec 7.5.3.7, recommends - * programming the same ASPM Control value for all functions of - * multi-function devices, so disable ASPM for all of them. + * Do not free the link state any earlier. If function 0 is a + * switch upstream port, this link state is parent_link to all + * subordinate ones. */ + if (pdev != link->downstream) + goto out; + pcie_config_aspm_link(link, 0); list_del(&link->sibling); free_link_state(link); @@ -1293,6 +1293,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev) pcie_config_aspm_path(parent_link); } + out: mutex_unlock(&aspm_lock); up_read(&pci_bus_sem); } |