On our Marvell OCTEON CN96XX board, we observed the following panic on the latest kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [0000000000000080] user address but active_mm is swapper Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: CPU: 9 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc7-00149-g9bffa1ad25b8 #1 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : of_pci_add_properties+0x278/0x4c8 lr : of_pci_add_properties+0x258/0x4c8 sp : ffff8000822ef9b0 x29: ffff8000822ef9b0 x28: ffff000106dd8000 x27: ffff800081bc3b30 x26: ffff800081540118 x25: ffff8000813d2be0 x24: 0000000000000000 x23: ffff00010528a800 x22: ffff000107c50000 x21: ffff0001039c2630 x20: ffff0001039c2630 x19: 0000000000000000 x18: ffffffffffffffff x17: 00000000a49c1b85 x16: 0000000084c07b58 x15: ffff000103a10f98 x14: ffffffffffffffff x13: ffff000103a10f96 x12: 0000000000000003 x11: 0101010101010101 x10: 000000000000002c x9 : ffff800080ca7acc x8 : ffff0001038fd900 x7 : 0000000000000000 x6 : 0000000000696370 x5 : 0000000000000000 x4 : 0000000000000002 x3 : ffff8000822efa40 x2 : ffff800081341000 x1 : ffff000107c50000 x0 : 0000000000000000 Call trace: of_pci_add_properties+0x278/0x4c8 (P) of_pci_make_dev_node+0xe0/0x158 pci_bus_add_device+0x158/0x210 pci_bus_add_devices+0x40/0x98 pci_host_probe+0x94/0x118 pci_host_common_probe+0x120/0x1a0 platform_probe+0x70/0xf0 really_probe+0xb4/0x2a8 __driver_probe_device+0x80/0x140 driver_probe_device+0x48/0x170 __driver_attach+0x9c/0x1b0 bus_for_each_dev+0x7c/0xe8 driver_attach+0x2c/0x40 bus_add_driver+0xec/0x218 driver_register+0x68/0x138 __platform_driver_register+0x2c/0x40 gen_pci_driver_init+0x24/0x38 do_one_initcall+0x4c/0x278 kernel_init_freeable+0x1f4/0x3d0 kernel_init+0x28/0x1f0 ret_from_fork+0x10/0x20 Code: aa1603e1 f0005522 d2800044 91000042 (f94040a0)

This regression was introduced by commit 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags"). On our board, the 002:00:07.0 bridge is misconfigured by the bootloader. Both its secondary and subordinate bus numbers are initialized to 0, while its fixed secondary bus number is set to 8. However, bus number 8 is also assigned to another bridge (0002:00:0f.0). Although this is a bootloader issue, before the change in commit 7246a4520b4b, the PCI_REASSIGN_ALL_BUS flag was set by default when PCI_PROBE_ONLY was enabled, ensuing that all the bus number for these bridges were reassigned, avoiding any conflicts.

After the change introduced in commit 7246a4520b4b, the bus numbers assigned by the bootloader are reused by all other bridges, except the misconfigured 002:00:07.0 bridge. The kernel attempt to reconfigure 002:00:07.0 by reusing the fixed secondary bus number 8 assigned by bootloader. However, since a pci_bus has already been allocated for bus 8 due to the probe of 0002:00:0f.0, no new pci_bus allocated for 002:00:07.0. This results in a pci bridge device without a pci_bus attached (pdev->subordinate == NULL). Consequently, accessing pdev->subordinate in of_pci_prop_bus_range() leads to a NULL pointer dereference.

To summarize, we need to restore the PCI_REASSIGN_ALL_BUS flag when PCI_PROBE_ONLY is enabled in order to work around issue like the one described above.

Cc: stable@vger.kernel.org Fixes: 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags") Signed-off-by: Bo Sun Bo.Sun.CN@windriver.com --- drivers/pci/controller/pci-host-common.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c index cf5f59a745b3..615923acbc3e 100644 --- a/drivers/pci/controller/pci-host-common.c +++ b/drivers/pci/controller/pci-host-common.c @@ -73,6 +73,10 @@ int pci_host_common_probe(struct platform_device *pdev) if (IS_ERR(cfg)) return PTR_ERR(cfg);

+ /* Do not reassign resources if probe only */ + if (!pci_has_flag(PCI_PROBE_ONLY)) + pci_add_flags(PCI_REASSIGN_ALL_BUS); + bridge->sysdata = cfg; bridge->ops = (struct pci_ops *)&ops->pci_ops; bridge->msi_domain = true;