kexec: fix Oops in crash_shrink_memory()

When crashkernel is not enabled, "echo 0 > /sys/kernel/kexec_crash_size"
OOPSes the kernel in crash_shrink_memory.  This happens when
crash_shrink_memory tries to release the 'crashk_res' resource which are
not reserved.  Also value of "/sys/kernel/kexec_crash_size" shows as 1,
which should be 0.

This patch fixes the OOPS in crash_shrink_memory and shows
"/sys/kernel/kexec_crash_size" as 0 when crash kernel memory is not
reserved.

Signed-off-by: Pavan Naregundi <pavan@linux.vnet.ibm.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 474a84715eaca2936b51ad5a6c46fb4774751c5b..131b1703936f6dbe71cf84c2ff572efef6c47e70 100644 (file)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1089,9 +1089,10 @@ void crash_kexec(struct pt_regs *regs)
 
 size_t crash_get_memory_size(void)
 {
-       size_t size;
+       size_t size = 0;
        mutex_lock(&kexec_mutex);
-       size = crashk_res.end - crashk_res.start + 1;
+       if (crashk_res.end != crashk_res.start)
+               size = crashk_res.end - crashk_res.start + 1;
        mutex_unlock(&kexec_mutex);
        return size;
 }
@@ -1134,7 +1135,7 @@ int crash_shrink_memory(unsigned long new_size)
 
        free_reserved_phys_range(end, crashk_res.end);
 
-       if (start == end)
+       if ((start == end) && (crashk_res.parent != NULL))
                release_resource(&crashk_res);
        crashk_res.end = end - 1;