[PATCH 4/6 v3] csky: Fix syscall_get_arguments() and syscall_set_arguments()

[Steven Rostedt]

From: "Dmitry V. Levin" <l...@altlinux.org>

C-SKY syscall arguments are located in orig_a0,a1,a2,a3,regs[0],regs[1]
fields of struct pt_regs.

Due to an off-by-one bug and a bug in pointer arithmetic
syscall_get_arguments() was reading orig_a0,regs[1..5] fields instead.
Likewise, syscall_set_arguments() was writing orig_a0,regs[1..5] fields
instead.

Link: http://lkml.kernel.org/r/20190329171230.gb32...@altlinux.org

Fixes: 4859bfca11c7d ("csky: System Call")
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Will Drewry <w...@chromium.org>
Cc: Guo Ren <guo...@kernel.org>
Cc: sta...@vger.kernel.org # v4.20+
Signed-off-by: Dmitry V. Levin <l...@altlinux.org>
Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org>
---
 arch/csky/include/asm/syscall.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/csky/include/asm/syscall.h b/arch/csky/include/asm/syscall.h
index d637445737b7..9a9cd81e66c1 100644
--- a/arch/csky/include/asm/syscall.h
+++ b/arch/csky/include/asm/syscall.h
@@ -49,10 +49,11 @@ syscall_get_arguments(struct task_struct *task, struct 
pt_regs *regs,
        if (i == 0) {
                args[0] = regs->orig_a0;
                args++;
-               i++;
                n--;
+       } else {
+               i--;
        }
-       memcpy(args, &regs->a1 + i * sizeof(regs->a1), n * sizeof(args[0]));
+       memcpy(args, &regs->a1 + i, n * sizeof(args[0]));
 }
 
 static inline void
@@ -63,10 +64,11 @@ syscall_set_arguments(struct task_struct *task, struct 
pt_regs *regs,
        if (i == 0) {
                regs->orig_a0 = args[0];
                args++;
-               i++;
                n--;
+       } else {
+               i--;
        }
-       memcpy(&regs->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
+       memcpy(&regs->a1 + i, args, n * sizeof(regs->a1));
 }
 
 static inline int
-- 
2.20.1