[PATCH 3.12 51/60] s390: TASK_SIZE for kernel threads

From: Jiri Slaby
Date: Tue Mar 14 2017 - 09:18:45 EST


From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

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

===============

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: Jiri Slaby <jslaby@xxxxxxx>
---
arch/s390/include/asm/processor.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index ca7821f07260..a42a05322d25 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -48,7 +48,8 @@ extern void execve_tail(void);

#else /* CONFIG_64BIT */

-#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)
--
2.12.0