[PATCH 1/2 v2] kernel/resource: Invalid memory access in __release_resource

[Ricardo Ribalda Delgado <ricardo.ribalda-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

When a resource is initialized via of_platform_populate.
resource->parent is initialized to NULL via kzalloc.
(of_platform_populate->of_device_alloc->of_address_to_resource)

If of_platform_depopulate is called later, resource->parent is
accessed (Offset 0x30 of address 0), causing a kernel error.

This patch evaluates resouce->parent before accessing it. If it
is not initialized, -EACCESS is returned.

Also a WARN is thrown, so the developer can have a hint about what
needs to be fixed.

Fixes:
BUG: unable to handle kernel NULL pointer deference at 0000000000000030
IP: release_resource+0x26/0x90
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 kernel/resource.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/resource.c b/kernel/resource.c
index 90552aa..b7b270f 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -237,6 +237,9 @@ static int __release_resource(struct resource *old)
 {
 	struct resource *tmp, **p;
 
+	if (WARN_ON(!old->parent))
+		return -EINVAL;
+
 	p = &old->parent->child;
 	for (;;) {
 		tmp = *p;
-- 
2.1.4

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