[PATCH] iommu/mediatek: Validate number of phandles associated with "mediatek, larbs"

[Guenter Roeck]

Since commit baf94e6ebff9 ("iommu/mediatek: Add device link for smi-common
and m4u"), the driver assumes that at least one phandle associated with
"mediatek,larbs" exists. If that is not the case, for example if reason
"mediatek,larbs" is provided as boolean property, the code will use an
uninitialized pointer and may crash. To fix the problem, ensure that the
number of phandles associated with "mediatek,larbs" is at least 1 and
bail out immediately if that is not the case.

Cc: Yong Wu <yong.wu at mediatek.com>
Cc: Tomasz Figa <tfiga at chromium.org>
Fixes: baf94e6ebff9 ("iommu/mediatek: Add device link for smi-common and m4u")
Reported-by: kernel test robot <lkp at intel.com>
Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
Signed-off-by: Guenter Roeck <linux at roeck-us.net>
---
 drivers/iommu/mtk_iommu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 25b834104790..0bbe32d0a2a6 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -828,6 +828,8 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 					     "mediatek,larbs", NULL);
 	if (larb_nr < 0)
 		return larb_nr;
+	if (larb_nr == 0)
+		return -EINVAL;
 
 	for (i = 0; i < larb_nr; i++) {
 		u32 id;
-- 
2.33.0