linux-kernel - [PATCH 3.10 063/319] MIPS: ptrace: Fix regs_return

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Message-Id: <1486322486-8024-34-git-send-email-w@1wt.eu>
Date:   Sun,  5 Feb 2017 20:20:50 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Marcin Nowakowski <marcin.nowakowski@...tec.com>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 063/319] MIPS: ptrace: Fix regs_return_value for kernel context

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: Willy Tarreau <w@....eu>
---
 arch/mips/include/asm/ptrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
index 5e6cd09..a288de2 100644
--- a/arch/mips/include/asm/ptrace.h
+++ b/arch/mips/include/asm/ptrace.h
@@ -73,7 +73,7 @@ static inline int is_syscall_success(struct pt_regs *regs)
 
 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];
-- 
2.8.0.rc2.1.gbe9624a