s390/mem_detect: add DAT sanity check

Add sanity check: verify if the passed in array resides in vmalloc space.
If so print a warning and return to caller.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/arch/s390/mm/mem_detect.c b/arch/s390/mm/mem_detect.c
index fb216e11c25d..854c08448de1 100644
--- a/arch/s390/mm/mem_detect.c
+++ b/arch/s390/mm/mem_detect.c
@@ -50,16 +50,28 @@ void detect_memory_layout(struct mem_chunk chunk[])
         unsigned long flags, flags_dat, cr0;
 
         memset(chunk, 0, MEMORY_CHUNKS * sizeof(struct mem_chunk));
-        /* Disable IRQs, DAT and low address protection so tprot does the
+        /*
+         * Disable IRQs, DAT and low address protection so tprot does the
          * right thing and we don't get scheduled away with low address
          * protection disabled.
          */
         local_irq_save(flags);
         flags_dat = __arch_local_irq_stnsm(0xfb);
+        /*
+         * In case DAT was enabled, make sure chunk doesn't reside in vmalloc
+         * space. We have disabled DAT and any access to vmalloc area will
+         * cause an exception.
+         * If DAT was disabled we are called from early ipl code.
+         */
+        if (test_bit(5, &flags_dat)) {
+                if (WARN_ON_ONCE(is_vmalloc_or_module_addr(chunk)))
+                        goto out;
+        }
         __ctl_store(cr0, 0, 0);
         __ctl_clear_bit(0, 28);
         find_memory_chunks(chunk);
         __ctl_load(cr0, 0, 0);
+out:
         __arch_local_irq_ssm(flags_dat);
         local_irq_restore(flags);
 }