[PATCH] mtd: lantiq-flash: Fix NULL pointer dereference in probe

[PATCH] mtd: lantiq-flash: Fix NULL pointer dereference in probe

[Guo Zihao]

ltq_mtd_probe() dereferences ltq_mtd->map->virt before the map_info
structure is allocated: the map pointer itself is still NULL when
ltq_mtd->map->virt is assigned, because the structure is allocated a
few lines below. Any device with a "lantiq,nor" compatible therefore
crashes the kernel with a NULL pointer dereference during probe.

Assign the mapping after the map_info allocation instead.

Fixes: 6145e07e9c77 ("mtd: lantiq-flash: Use devm_platform_get_and_ioremap_resource()")
Cc: stable@vger.kernel.org
Signed-off-by: Guo Zihao <guozh23@xiaopeng.com>
---
 drivers/mtd/maps/lantiq-flash.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/maps/lantiq-flash.c b/drivers/mtd/maps/lantiq-flash.c
index 80d467eba..5c2ace302 100644
--- a/drivers/mtd/maps/lantiq-flash.c
+++ b/drivers/mtd/maps/lantiq-flash.c
@@ -118,15 +118,15 @@ ltq_mtd_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, ltq_mtd);
 
-	ltq_mtd->map->virt = devm_platform_get_and_ioremap_resource(pdev, 0, &ltq_mtd->res);
-	if (IS_ERR(ltq_mtd->map->virt))
-		return PTR_ERR(ltq_mtd->map->virt);
-
 	ltq_mtd->map = devm_kzalloc(&pdev->dev, sizeof(struct map_info),
 				    GFP_KERNEL);
 	if (!ltq_mtd->map)
 		return -ENOMEM;
 
+	ltq_mtd->map->virt = devm_platform_get_and_ioremap_resource(pdev, 0, &ltq_mtd->res);
+	if (IS_ERR(ltq_mtd->map->virt))
+		return PTR_ERR(ltq_mtd->map->virt);
+
 	ltq_mtd->map->phys = ltq_mtd->res->start;
 	ltq_mtd->map->size = resource_size(ltq_mtd->res);
 
-- 
2.50.1