[PATCH] mtd: nand: fix NULL pointer dereference in of_get_nand_ecc_algo

["Rafał Miłecki" <zajec5@gmail.com>]

Our array nand_ecc_algos doesn't specify mappings for all available
enum nand_ecc_algo values. The one missing there is NAND_ECC_UNKNOWN
as this value is reserved for algorithm not being specified at all.
It means we have to be careful when iterating this array and handle
NULL values.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
---
Hi Boris,

Sorry for this crash in nand subsystem :( If you think it's OK you may
pick this patch as a fixup for
c6e002a7ca9f ("mtd: nand: add support for "nand-ecc-algo" DT property")
---
 drivers/mtd/nand/nand_base.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index a5417a0..0eaa9dc 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -4016,6 +4016,8 @@ static int of_get_nand_ecc_algo(struct device_node *np)
 	err = of_property_read_string(np, "nand-ecc-algo", &pm);
 	if (!err) {
 		for (i = 0; i < ARRAY_SIZE(nand_ecc_algos); i++)
+			if (!nand_ecc_algos[i])
+				continue;
 			if (!strcasecmp(pm, nand_ecc_algos[i]))
 				return i;
 		return -ENODEV;
-- 
1.8.4.5