linux-kernel - [PATCH] riscv: fix syscall_get_arguments() and syscall_set

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Message-ID: <20190329171221.GA32456@altlinux.org>
Date:   Fri, 29 Mar 2019 20:12:21 +0300
From:   "Dmitry V. Levin" <ldv@...linux.org>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] riscv: fix syscall_get_arguments() and
 syscall_set_arguments()

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.

Fixes: e2c0cdfba7f69 ("RISC-V: User-facing API")
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Will Drewry <wad@...omium.org>
Cc: linux-riscv@...ts.infradead.org
Cc: stable@...r.kernel.org # v4.15+
Signed-off-by: Dmitry V. Levin <ldv@...linux.org>
---
 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)
-- 
ldv