[PATCH 4.4 09/36] s390: TASK_SIZE for kernel threads

From: Greg Kroah-Hartman
Date: Mon Mar 13 2017 - 04:42:16 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

commit fb94a687d96c570d46332a4a890f1dcb7310e643 upstream.

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.

Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/s390/include/asm/processor.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -74,7 +74,8 @@ 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)