linux-kernel - [tip:x86/urgent] x86/mpx: Fix off-by-one comparison with nr

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Message-ID: <tip-9bf148cb0812595bfdf5100bd2c07e9bec9c6ef5@git.kernel.org>
Date:	Fri, 26 Feb 2016 13:15:43 -0800
From:	tip-bot for Colin Ian King <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	kirill.shutemov@...ux.intel.com, bp@...en8.de, hpa@...or.com,
	mingo@...nel.org, linux-kernel@...r.kernel.org,
	colin.king@...onical.com, tglx@...utronix.de,
	dave.hansen@...ux.intel.com
Subject: [tip:x86/urgent] x86/mpx: Fix off-by-one comparison with
 nr_registers

Commit-ID:  9bf148cb0812595bfdf5100bd2c07e9bec9c6ef5
Gitweb:     http://git.kernel.org/tip/9bf148cb0812595bfdf5100bd2c07e9bec9c6ef5
Author:     Colin Ian King <colin.king@...onical.com>
AuthorDate: Fri, 26 Feb 2016 18:55:31 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 26 Feb 2016 22:12:47 +0100

x86/mpx: Fix off-by-one comparison with nr_registers

In the unlikely event that regno == nr_registers then we get an array
overrun on regoff because the invalid register check is currently
off-by-one. Fix this with a check that regno is >= nr_registers instead.

Detected with static analysis using CoverityScan.

Fixes: fcc7ffd67991 "x86, mpx: Decode MPX instruction to get bound violation information"
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/1456512931-3388-1-git-send-email-colin.king@canonical.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/mm/mpx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index b2fd67d..ef05755 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -123,7 +123,7 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
 		break;
 	}
 
-	if (regno > nr_registers) {
+	if (regno >= nr_registers) {
 		WARN_ONCE(1, "decoded an instruction with an invalid register");
 		return -EINVAL;
 	}