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

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Message-Id: <1456512931-3388-1-git-send-email-colin.king@canonical.com>
Date:	Fri, 26 Feb 2016 18:55:31 +0000
From:	Colin King <colin.king@...onical.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H . Peter Anvin" <hpa@...ux.intel.com>, x86@...nel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] x86/mpx: Fix off-by-one comparison with nr_registers

From: Colin Ian King <colin.king@...onical.com>

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.

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 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 5584397..8047687 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;
 	}
-- 
2.7.0