[PATCH] mtd: rawnand: intel: Fix potential buffer overflow in probe

[Evgeny Novikov]

ebu_nand_probe() read the value of u32 variable "cs" from the device
firmware description and used it as the index for array ebu_host->cs
that can contain MAX_CS (2) elements at most. That could result in
a buffer overflow and various bad consequences later.

Fix the potential buffer overflow by restricting values of "cs" with
MAX_CS in probe.

Found by Linux Driver Verification project (linuxtesting.org).

Fixes: 0b1039f016e8 ("mtd: rawnand: Add NAND controller support on Intel LGM SoC")
Signed-off-by: Evgeny Novikov <novikov at ispras.ru>
Co-developed-by: Kirill Shilimanov <kirill.shilimanov at huawei.com>
Signed-off-by: Kirill Shilimanov <kirill.shilimanov at huawei.com>
Co-developed-by: Anton Vasilyev <vasilyev at ispras.ru>
Signed-off-by: Anton Vasilyev <vasilyev at ispras.ru>
---
 drivers/mtd/nand/raw/intel-nand-controller.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mtd/nand/raw/intel-nand-controller.c b/drivers/mtd/nand/raw/intel-nand-controller.c
index 8b49fd56cf96..81678088fdca 100644
--- a/drivers/mtd/nand/raw/intel-nand-controller.c
+++ b/drivers/mtd/nand/raw/intel-nand-controller.c
@@ -609,6 +609,11 @@ static int ebu_nand_probe(struct platform_device *pdev)
 		dev_err(dev, "failed to get chip select: %d\n", ret);
 		return ret;
 	}
+	if (cs >= MAX_CS) {
+		dev_err(dev, "got invalid chip select: %d\n", cs);
+		return -EINVAL;
+	}
+
 	ebu_host->cs_num = cs;
 
 	resname = devm_kasprintf(dev, GFP_KERNEL, "nand_cs%d", cs);
-- 
2.26.2