libnvdimm/labels: Fix divide error in nd_label_data_init()

Robert Richter · weiny2 · commit ef1d3455bbc1 · 2025-03-20T16:54:27.000-05:00
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
@@ -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;
