linux-kernel - [PATCH 3.19 v2 1/3] x86: Fix off-by-one in the instruction decoder length checks

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Message-Id: <602a94627fedaab4e339088d633b72174caf14c9.1421103159.git.luto@amacapital.net>
Date:	Mon, 12 Jan 2015 15:04:09 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: [PATCH 3.19 v2 1/3] x86: Fix off-by-one in the instruction decoder length checks

If next_byte + sizeof(t) == end_kaddr, then we are trying to read
exactly to the end; this should be allowed.

Fixes: 6ba48ff46f76 x86: Remove arbitrary instruction size limit in instruction decoder
Signed-off-by: Andy Lutomirski <luto@...capital.net>
---
 arch/x86/lib/insn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 2480978b31cc..1313ae6b478b 100644
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -28,7 +28,7 @@
 
 /* Verify next sizeof(t) bytes can be on the same instruction */
 #define validate_next(t, insn, n)	\
-	((insn)->next_byte + sizeof(t) + n < (insn)->end_kaddr)
+	((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
 
 #define __get_next(t, insn)	\
 	({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; })
-- 
2.1.0

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