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kdump: crashk_res init check for /sys/kernel/kexec_crash_size

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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".

In addition to that this patch also simplifies the "ret = -EINVAL" vs.
"ret = 0" logic as suggested by Simon Horman.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Reviewed-by: Dave Young <dyoung@redhat.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michael Holzheu 2012-01-12 17:20:15 -08:00 committed by Linus Torvalds
parent 6480e5a092
commit bec013c40b
1 changed files with 4 additions and 5 deletions
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9
kernel/kexec.c
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@ -1129,6 +1129,7 @@ int crash_shrink_memory(unsigned long new_size)
{
int ret = 0;
unsigned long start, end;
unsigned long old_size;
struct resource *ram_res;
mutex_lock(&kexec_mutex);
@ -1139,11 +1140,9 @@ int crash_shrink_memory(unsigned long new_size)
}
start = crashk_res.start;
end = crashk_res.end;
if (new_size >= end - start + 1) {
ret = -EINVAL;
if (new_size == end - start + 1)
ret = 0;
old_size = (end == 0) ? 0 : end - start + 1;
if (new_size >= old_size) {
ret = (new_size == old_size) ? 0 : -EINVAL;
goto unlock;
}