Cc: Hou Zhiqiang <Zhiqiang.Hou@xxxxxxx> I found that this patch would cause null pointer dereference exception when removing the function link. If once linking the test function to the controller, # ln -s functions/pci_epf_test/test controllers/66000000.pcie-ep/ and unlinking it immediately, # rm controllers/66000000.pcie-ep/test then the driver will occur null pointer access in dw_pcie_ep_clear_bar() because ep->ib_window_map doesn't have a pointer to allocated memory yet. To fix the original issue, I strongly recommend to apply Hou's patch [1] instead of this patch. Thank you, [1] https://patchwork.kernel.org/project/linux-pci/patch/20210125044803.4310-1-Zhiqiang.Hou@xxxxxxx/ On 2021/01/21 0:20, Rob Herring wrote:
On Mon, Jan 18, 2021 at 5:10 PM Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx> wrote:The commit 281f1f99cf3a ("PCI: dwc: Detect number of iATU windows") gets the values of pci->num_ib_windows and pci->num_ob_windows from iATU registers instead of DT properties in dw_pcie_iatu_detect_regions*() or its unroll version. However, before the values are set, the allocations in dw_pcie_ep_init() refer them to determine the sizes of window_map. As a result, null pointer dereference exception will occur when linking the EP function and the controller. # ln -s functions/pci_epf_test/test controllers/66000000.pcie-ep/ Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 The call trace is as follows: Call trace: _find_next_bit.constprop.1+0xc/0x88 dw_pcie_ep_set_bar+0x78/0x1f8 pci_epc_set_bar+0x9c/0xe8 pci_epf_test_core_init+0xe8/0x220 pci_epf_test_bind+0x1e0/0x378 pci_epf_bind+0x54/0xb0 pci_epc_epf_link+0x58/0x80 configfs_symlink+0x1c0/0x570 vfs_symlink+0xdc/0x198 do_symlinkat+0xa0/0x110 __arm64_sys_symlinkat+0x28/0x38 el0_svc_common+0x84/0x1a0 do_el0_svc+0x38/0x88 el0_svc+0x1c/0x28 el0_sync_handler+0x88/0xb0 el0_sync+0x140/0x180 The pci->num_{ib,ob}_windows should be referenced after they are set by dw_pcie_iatu_detect_regions*() called from dw_pcie_setup(). Cc: Rob Herring <robh@xxxxxxxxxx> Fixes: 281f1f99cf3a ("PCI: dwc: Detect number of iATU windows") Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx> --- drivers/pci/controller/dwc/pcie-designware-ep.c | 41 ++++++++++++------------- 1 file changed, 20 insertions(+), 21 deletions(-)Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
-- --- Best Regards Kunihiko Hayashi
