kernel/resource: fix return code check in __request_free_mem_region

Splitting an earlier version of a patch that allowed calling
__request_region() while holding the resource lock into a series of
patches required changing the return code for the newly introduced
__request_region_locked().

Unfortunately this change was not carried through to a subsequent commit
56fd94919b ("kernel/resource: fix locking in request_free_mem_region")
in the series.  This resulted in a use-after-free due to freeing the
struct resource without properly releasing it.  Fix this by correcting the
return code check so that the struct is not freed if the request to add it
was successful.

Link: https://lkml.kernel.org/r/20210512073528.22334-1-apopple@nvidia.com
Fixes: 56fd94919b ("kernel/resource: fix locking in request_free_mem_region")
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Muchun Song <smuchun@gmail.com>
Cc: Oliver Sang <oliver.sang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/resource.c

@@ -1805,7 +1805,7 @@ static struct resource *__request_free_mem_region(struct device *dev,
 				REGION_DISJOINT)
 			continue;
 
-		if (!__request_region_locked(res, &iomem_resource, addr, size,
+		if (__request_region_locked(res, &iomem_resource, addr, size,
 						name, 0))
 			break;