libnvdimm/labels: Fix divide error in nd_label_data_init()

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:nd_label_data_init+0x10e/0x800 [libnvdimm]

Code and flow:

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

drivers/cxl/pmem.c:             .config_size = mds->lsa_size,

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

drivers/nvdimm/label.c: max_xfer = min_t(size_t, ndd->nsarea.max_xfer, config_size);

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

drivers/nvdimm/label.c: /* Make our initial read size a multiple of max_xfer size */
drivers/nvdimm/label.c: read_size = min(DIV_ROUND_UP(read_size, max_xfer) * max_xfer,
drivers/nvdimm/label.c-                 config_size);

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

Signed-off-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://patch.msgid.link/20250320112223.608320-1-rrichter@amd.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

diff --git a/drivers/nvdimm/label.c b/drivers/nvdimm/label.c
index 082253a3a9560778c4ddaaaebacd4c3a6a8c72d0..04f4a049599a1a02f1fe16822b8ef10c9e6b3299 100644 (file)
--- a/drivers/nvdimm/label.c
+++ b/drivers/nvdimm/label.c
@@ -442,7 +442,8 @@ int nd_label_data_init(struct nvdimm_drvdata *ndd)
        if (ndd->data)
                return 0;
 
-       if (ndd->nsarea.status || ndd->nsarea.max_xfer == 0) {
+       if (ndd->nsarea.status || ndd->nsarea.max_xfer == 0 ||
+           ndd->nsarea.config_size == 0) {
                dev_dbg(ndd->dev, "failed to init config data area: (%u:%u)\n",
                        ndd->nsarea.max_xfer, ndd->nsarea.config_size);
                return -ENXIO;