kexec: fix OOPS in crash_kernel_shrink

Two "echo 0 > /sys/kernel/kexec_crash_size" OOPSes kernel.  Also content
of this file is invalid after first shrink to zero: it shows 1 instead of
0.

This scenario is unlikely to happen often (root privs, valid crashkernel=
in cmdline, dump-capture kernel not loaded), I hit it only by chance.

This patch fixes it.

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Cc: Cong Wang <amwang@redhat.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 87ebe8adc47..474a84715ea 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1134,11 +1134,9 @@ int crash_shrink_memory(unsigned long new_size)
 
         free_reserved_phys_range(end, crashk_res.end);
 
-        if (start == end) {
-                crashk_res.end = end;
+        if (start == end)
                 release_resource(&crashk_res);
-        } else
-                crashk_res.end = end - 1;
+        crashk_res.end = end - 1;
 
 unlock:
         mutex_unlock(&kexec_mutex);