kexec: clear crashk_res if all its memory has been released

If the resource of crashk_res has been released, it is better to clear crashk_res.start and crashk_res.end. Because 'end = start - 1' is not reasonable, and in some places the test is based on crashk_res.end, not resource_size(&crashk_res). Link: https://lkml.kernel.org/r/20230527123439.772-4-thunder.leizhen@huawei.com Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Acked-by: Baoquan He <bhe@redhat.com> Cc: Cong Wang <amwang@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Zhen Lei

kernel/kexec_core.c

@@ -1137,15 +1137,18 @@ int crash_shrink_memory(unsigned long new_size)
 end = start + new_size;
 crash_free_reserved_phys_range(end, crashk_res.end);
 
-if (start == end)
-release_resource(&crashk_res);
-
 ram_res->start = end;
 ram_res->end = crashk_res.end;
 ram_res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM;
 ram_res->name = "System RAM";
 
-crashk_res.end = end - 1;
+if (start == end) {
+release_resource(&crashk_res);
+crashk_res.start = 0;
+crashk_res.end = 0;
+} else {
+crashk_res.end = end - 1;
+}
 
 insert_resource(&iomem_resource, ram_res);