linux-kernel - [PATCH 4.4 053/112] MIPS: ptrace: Fix regs_return

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Message-Id: <20161026122307.043285041@linuxfoundation.org>
Date:   Wed, 26 Oct 2016 14:22:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Marcin Nowakowski <marcin.nowakowski@...tec.com>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 4.4 053/112] MIPS: ptrace: Fix regs_return_value for kernel context

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

------------------

From: Marcin Nowakowski <marcin.nowakowski@...tec.com>

commit 74f1077b5b783e7bf4fa3007cefdc8dbd6c07518 upstream.

Currently regs_return_value always negates reg[2] if it determines
the syscall has failed, but when called in kernel context this check is
invalid and may result in returning a wrong value.

This fixes errors reported by CONFIG_KPROBES_SANITY_TEST

Fixes: d7e7528bcd45 ("Audit: push audit success and retcode into arch ptrace.h")
Signed-off-by: Marcin Nowakowski <marcin.nowakowski@...tec.com>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14381/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/include/asm/ptrace.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/mips/include/asm/ptrace.h
+++ b/arch/mips/include/asm/ptrace.h
@@ -152,7 +152,7 @@ static inline int is_syscall_success(str
 
 static inline long regs_return_value(struct pt_regs *regs)
 {
-	if (is_syscall_success(regs))
+	if (is_syscall_success(regs) || !user_mode(regs))
 		return regs->regs[2];
 	else
 		return -regs->regs[2];