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Message-Id: <20190401134420.958530155@goodmis.org>
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Date:   Mon, 01 Apr 2019 09:41:07 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     linux-kernel@vger.kernel.org
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Roland McGrath <roland@hack.frob.com>,
        Oleg Nesterov <oleg@redhat.com>, linux-arch@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Andy Lutomirski <luto@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Palmer Dabbelt <palmer@sifive.com>,
        Will Drewry <wad@chromium.org>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv@lists.infradead.org
Subject: [PATCH 3/6 v3] riscv: Fix syscall_get_arguments() and syscall_set_arguments()
References: <20190401134104.676620247@goodmis.org>
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From: "Dmitry V. Levin" <ldv@altlinux.org>

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@altlinux.org

Fixes: e2c0cdfba7f69 ("RISC-V: User-facing API")
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: linux-riscv@lists.infradead.org
Cc: stable@vger.kernel.org # v4.15+
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.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)
-- 
2.20.1