CVE-2025-38072: libnvdimm/labels: Fix divide error in nd_label_data_init()

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

libnvdimm/labels: Fix divide error in ndlabeldatainit()

If a faulty CXL memory device returns a broken zero LSA size in its memory device information (Identify Memory Device (Opcode 4000h), CXL spec. 3.1, 8.2.9.9.1.1), a divide error occurs in the libnvdimm driver:

Oops: divide error: 0000 [#1] PREEMPT SMP NOPTI RIP: 0010:ndlabeldatainit+0x10e/0x800 [libnvdimm]

Code and flow:

1) CXL Command 4000h returns LSA size = 0 2) configsize is assigned to zero LSA size (CXL pmem driver):

drivers/cxl/pmem.c: .configsize = mds->lsasize,

3) maxxfer is set to zero (nvdimm driver):

drivers/nvdimm/label.c: maxxfer = mint(sizet, ndd->nsarea.maxxfer, configsize);

4) A subsequent DIVROUNDUP() causes a division by zero:

drivers/nvdimm/label.c: / Make our initial read size a multiple of maxxfer size / drivers/nvdimm/label.c: readsize = min(DIVROUNDUP(readsize, maxxfer) maxxfer, drivers/nvdimm/label.c- configsize);

Fix this by checking the config size parameter by extending an existing check.