s390: TASK_SIZE for kernel threads
Return a sensible value if TASK_SIZE if called from a kernel thread.
This gets us around an issue with copy_mount_options that does a magic
size calculation "TASK_SIZE - (unsigned long)data" while in a kernel
thread and data pointing to kernel space.
Cc: <stable@vger.kernel.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index c57c5c2..e498871 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -91,7 +91,8 @@ extern void execve_tail(void);
* User space process size: 2GB for 31 bit, 4TB or 8PT for 64 bit.
*/
-#define TASK_SIZE_OF(tsk) ((tsk)->mm->context.asce_limit)
+#define TASK_SIZE_OF(tsk) ((tsk)->mm ? \
+ (tsk)->mm->context.asce_limit : TASK_MAX_SIZE)
#define TASK_UNMAPPED_BASE (test_thread_flag(TIF_31BIT) ? \
(1UL << 30) : (1UL << 41))
#define TASK_SIZE TASK_SIZE_OF(current)