linux-kernel - [PATCH AUTOSEL 6.1 029/212] libnvdimm/labels: Fix divide error in nd_label_data

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Message-Id: <20250505230624.2692522-29-sashal@kernel.org>
Date: Mon,  5 May 2025 19:03:21 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Robert Richter <rrichter@....com>,
	Pankaj Gupta <pankaj.gupta@....com>,
	Ira Weiny <ira.weiny@...el.com>,
	Sasha Levin <sashal@...nel.org>,
	dan.j.williams@...el.com,
	vishal.l.verma@...el.com,
	dave.jiang@...el.com,
	nvdimm@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.1 029/212] libnvdimm/labels: Fix divide error in nd_label_data_init()

From: Robert Richter <rrichter@....com>

[ Upstream commit ef1d3455bbc1922f94a91ed58d3d7db440652959 ]

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@....com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@....com>
Reviewed-by: Ira Weiny <ira.weiny@...el.com>
Link: https://patch.msgid.link/20250320112223.608320-1-rrichter@amd.com
Signed-off-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 082253a3a9560..04f4a049599a1 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