[tip:x86/urgent] x86/mpx: Fix off-by-one comparison with nr_registers

From: tip-bot for Colin Ian King
Date: Fri Feb 26 2016 - 16:16:27 EST

Commit-ID: 9bf148cb0812595bfdf5100bd2c07e9bec9c6ef5
Gitweb: http://git.kernel.org/tip/9bf148cb0812595bfdf5100bd2c07e9bec9c6ef5
Author: Colin Ian King <colin.king@xxxxxxxxxxxxx>
AuthorDate: Fri, 26 Feb 2016 18:55:31 +0000
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1456512931-3388-1-git-send-email-colin.king@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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,

- if (regno > nr_registers) {
+ if (regno >= nr_registers) {
WARN_ONCE(1, "decoded an instruction with an invalid register");
return -EINVAL;