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    Subject[PATCH] kdump: crashk_res init check for /sys/kernel/kexec_crash_size
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    Date
    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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