[PATCH] mtd: rawnand: mtk: avoid underflow in mtk_nfc_nand_chip_init()

[Evgeny Novikov]

If of_get_property() will set nsels to negative values the driver may
allocate insufficient memory for chip. Moreover, there may be underflow
for devm_kzalloc(). This can result in various bad consequences later.
The patch causes mtk_nfc_nand_chip_init() to fail for negative values of
nsels.

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

Signed-off-by: Evgeny Novikov <novi...@ispras.ru>
---
 drivers/mtd/nand/raw/mtk_nand.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/mtk_nand.c b/drivers/mtd/nand/raw/mtk_nand.c
index ad1b55dab211..df98a2eec240 100644
--- a/drivers/mtd/nand/raw/mtk_nand.c
+++ b/drivers/mtd/nand/raw/mtk_nand.c
@@ -1376,7 +1376,7 @@ static int mtk_nfc_nand_chip_init(struct device *dev, 
struct mtk_nfc *nfc,
                return -ENODEV;
 
        nsels /= sizeof(u32);
-       if (!nsels || nsels > MTK_NAND_MAX_NSELS) {
+       if (nsels <= 0 || nsels > MTK_NAND_MAX_NSELS) {
                dev_err(dev, "invalid reg property size %d\n", nsels);
                return -EINVAL;
        }
-- 
2.26.2