CVE-2024-41085

In the Linux kernel, the following vulnerability has been resolved:

cxl/mem: Fix no cxl_nvd during pmem region auto-assembling

When CXL subsystem is auto-assembling a pmem region during cxl

endpoint port probing, always hit below calltrace.

BUG: kernel NULL pointer dereference, address: 0000000000000078

#PF: supervisor read access in kernel mode

#PF: error_code(0x0000) - not-present page

RIP: 0010:cxl_pmem_region_probe+0x22e/0x360 [cxl_pmem]

Call Trace:

<TASK>

? __die+0x24/0x70

? page_fault_oops+0x82/0x160

? do_user_addr_fault+0x65/0x6b0

? exc_page_fault+0x7d/0x170

? asm_exc_page_fault+0x26/0x30

? cxl_pmem_region_probe+0x22e/0x360 [cxl_pmem]

? cxl_pmem_region_probe+0x1ac/0x360 [cxl_pmem]

cxl_bus_probe+0x1b/0x60 [cxl_core]

really_probe+0x173/0x410

? __pfx___device_attach_driver+0x10/0x10

__driver_probe_device+0x80/0x170

driver_probe_device+0x1e/0x90

__device_attach_driver+0x90/0x120

bus_for_each_drv+0x84/0xe0

__device_attach+0xbc/0x1f0

bus_probe_device+0x90/0xa0

device_add+0x51c/0x710

devm_cxl_add_pmem_region+0x1b5/0x380 [cxl_core]

cxl_bus_probe+0x1b/0x60 [cxl_core]

The cxl_nvd of the memdev needs to be available during the pmem region

probe. Currently the cxl_nvd is registered after the endpoint port probe.

The endpoint probe, in the case of autoassembly of regions, can cause a

pmem region probe requiring the not yet available cxl_nvd. Adjust the

sequence so this dependency is met.

This requires adding a port parameter to cxl_find_nvdimm_bridge() that

can be used to query the ancestor root port. The endpoint port is not

yet available, but will share a common ancestor with its parent, so

start the query from there instead.