Commit 666e7f9d authored May 07, 2023 by Ding Hui Committed by Greg Kroah-Hartman Jul 27, 2023

PCI/ASPM: Disable ASPM on MFD function removal to avoid use-after-free



[ Upstream commit 456d8aa37d0f56fc9e985e812496e861dcd6f2f2 ]

Struct pcie_link_state->downstream is a pointer to the pci_dev of function
0.  Previously we retained that pointer when removing function 0, and
subsequent ASPM policy changes dereferenced it, resulting in a
use-after-free warning from KASAN, e.g.:

  # echo 1 > /sys/bus/pci/devices/0000:03:00.0/remove
  # echo powersave > /sys/module/pcie_aspm/parameters/policy

  BUG: KASAN: slab-use-after-free in pcie_config_aspm_link+0x42d/0x500
  Call Trace:
   kasan_report+0xae/0xe0
   pcie_config_aspm_link+0x42d/0x500
   pcie_aspm_set_policy+0x8e/0x1a0
   param_attr_store+0x162/0x2c0
   module_attr_store+0x3e/0x80

PCIe spec r6.0, sec 7.5.3.7, recommends that software program the same ASPM
Control value in all functions of multi-function devices.

Disable ASPM and free the pcie_link_state when any child function is
removed so we can discard the dangling pcie_link_state->downstream pointer
and maintain the same ASPM Control configuration for all functions.

[bhelgaas: commit log and comment]
Debugged-by: Zongquan Qin <qinzongquan@sangfor.com.cn>
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Fixes: b5a0a9b5 ("PCI/ASPM: Read and set up L1 substate capabilities")
Link: https://lore.kernel.org/r/20230507034057.20970-1-dinghui@sangfor.com.cn


Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 961c8370

drivers/pci/pcie/aspm.c

+12 −9

Original line number	Diff line number	Diff line
		@@ -991,21 +991,24 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)

		down_read(&pci_bus_sem);
		mutex_lock(&aspm_lock);
		/*
		* All PCIe functions are in one slot, remove one function will remove
		* the whole slot, so just wait until we are the last function left.
		*/
		if (!list_empty(&parent->subordinate->devices))
		goto out;

		link = parent->link_state;
		root = link->root;
		parent_link = link->parent;

		/* All functions are removed, so just disable ASPM for the link */
		/*
		* 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.
		*
		* 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.
		*/
		pcie_config_aspm_link(link, 0);
		list_del(&link->sibling);
		/* Clock PM is for endpoint device */
		free_link_state(link);

		/* Recheck latencies and configure upstream links */
		@@ -1013,7 +1016,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
		pcie_update_aspm_capable(root);
		pcie_config_aspm_path(parent_link);
		}
		out:

		mutex_unlock(&aspm_lock);
		up_read(&pci_bus_sem);
		}