[PATCH 4.4 148/159] media: isif: fix a NULL pointer dereference bug

From: Greg Kroah-Hartman
Date: Fri Nov 22 2019 - 05:37:59 EST

From: Wenwen Wang <wang6495@xxxxxxx>

[ Upstream commit a26ac6c1bed951b2066cc4b2257facd919e35c0b ]

In isif_probe(), there is a while loop to get the ISIF base address and
linearization table0 and table1 address. In the loop body, the function
platform_get_resource() is called to get the resource. If
platform_get_resource() returns NULL, the loop is terminated and the
execution goes to 'fail_nobase_res'. Suppose the loop is terminated at the
first iteration because platform_get_resource() returns NULL and the
execution goes to 'fail_nobase_res'. Given that there is another while loop
at 'fail_nobase_res' and i equals to 0, one iteration of the second while
loop will be executed. However, the second while loop does not check the
return value of platform_get_resource(). This can cause a NULL pointer
dereference bug if the return value is a NULL pointer.

This patch avoids the above issue by adding a check in the second while
loop after the call to platform_get_resource().

Signed-off-by: Wenwen Wang <wang6495@xxxxxxx>
Signed-off-by: Hans Verkuil <hverkuil@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/media/platform/davinci/isif.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/davinci/isif.c b/drivers/media/platform/davinci/isif.c
index 99faea2e84c6b..78e37cf3470f2 100644
--- a/drivers/media/platform/davinci/isif.c
+++ b/drivers/media/platform/davinci/isif.c
@@ -1106,7 +1106,8 @@ static int isif_probe(struct platform_device *pdev)

while (i >= 0) {
res = platform_get_resource(pdev, IORESOURCE_MEM, i);
- release_mem_region(res->start, resource_size(res));
+ if (res)
+ release_mem_region(res->start, resource_size(res));