[PATCH 3/6 v3] riscv: Fix syscall_get_arguments() and syscall_set_arguments()

From: Steven Rostedt
Date: Mon Apr 01 2019 - 09:44:26 EST


From: "Dmitry V. Levin" <ldv@xxxxxxxxxxxx>

RISC-V syscall arguments are located in orig_a0,a1..a5 fields
of struct pt_regs.

Due to an off-by-one bug and a bug in pointer arithmetic
syscall_get_arguments() was reading s3..s7 fields instead of a1..a5.
Likewise, syscall_set_arguments() was writing s3..s7 fields
instead of a1..a5.

Link: http://lkml.kernel.org/r/20190329171221.GA32456@xxxxxxxxxxxx

Fixes: e2c0cdfba7f69 ("RISC-V: User-facing API")
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # v4.15+
Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
arch/riscv/include/asm/syscall.h | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index bba3da6ef157..6ea9e1804233 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -79,10 +79,11 @@ static inline void syscall_get_arguments(struct task_struct *task,
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 syscall_set_arguments(struct task_struct *task,
@@ -94,10 +95,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
if (i == 0) {
regs->orig_a0 = args[0];
args++;
- i++;
n--;
- }
- memcpy(&regs->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
+ } else {
+ i--;
+ }
+ memcpy(&regs->a1 + i, args, n * sizeof(regs->a1));
}

static inline int syscall_get_arch(void)
--
2.20.1