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Subject[PATCH] kdump: crashk_res init check for /sys/kernel/kexec_crash_size
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From: Michael Holzheu <holzheu@linux.vnet.ibm.com>

Currently it is possible to set the crash_size via the sysfs
/sys/kernel/kexec_crash_size even if no crash kernel memory has
been defined with the "crashkernel" parameter. In this case
"crashk_res" is not initialized and crashk_res.start = crashk_res.end = 0.
Unfortunately resource_size(&crashk_res) returns 1 in this case.
This breaks the s390 implementation of crash_(un)map_reserved_pages().

To fix the problem the correct "old_size" is now calculated in
crash_shrink_memory(). "old_size is set to "0" if crashk_res is
not initialized. With this change crash_shrink_memory() will do nothing,
when "crashk_res" is not initialized. It will return "0" for
"echo 0 > /sys/kernel/kexec_crash_size" and -EINVAL for
"echo [not zero] > /sys/kernel/kexec_crash_size".
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
---
kernel/kexec.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1131,7 +1131,7 @@ void __weak crash_free_reserved_phys_ran
int crash_shrink_memory(unsigned long new_size)
{
int ret = 0;
- unsigned long start, end;
+ unsigned long start, end, old_size;

mutex_lock(&kexec_mutex);

@@ -1141,10 +1141,10 @@ int crash_shrink_memory(unsigned long ne
}
start = crashk_res.start;
end = crashk_res.end;
-
- if (new_size >= end - start + 1) {
+ old_size = (end == 0) ? 0 : end - start + 1;
+ if (new_size >= old_size) {
ret = -EINVAL;
- if (new_size == end - start + 1)
+ if (new_size == old_size)
ret = 0;
goto unlock;
}



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