[PATCH v2] libnvdimm/labels: Fix divide error in nd_label_data_init()

[PATCH v2] libnvdimm/labels: Fix divide error in nd_label_data_init()

[Robert Richter]

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>
---
v2:
 * modified description to correct the instruction that is causing
   the div by zero (Ira)
 * updated tags
---
 drivers/nvdimm/label.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/label.c b/drivers/nvdimm/label.c
index 082253a3a956..04f4a049599a 100644
--- 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;
-- 
2.39.5

Re: [PATCH v2] libnvdimm/labels: Fix divide error in nd_label_data_init()

[Davidlohr Bueso]

On Thu, 20 Mar 2025, Robert Richter wrote:

>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>

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>

Re: [PATCH v2] libnvdimm/labels: Fix divide error in nd_label_data_init()

[Ira Weiny]

Robert Richter wrote:
> 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>

Applied to nvdimm/next

Thanks,
Ira

[snip]