From: Ding Hui dinghui@sangfor.com.cn
[ 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: b5a0a9b59c81 ("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 --- drivers/pci/pcie/aspm.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index 4b4184563a927..74b8183c305df 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -1010,21 +1010,24 @@ 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 */ @@ -1032,7 +1035,7 @@ 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); }