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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@canonical.com>
AuthorDate: Fri, 26 Feb 2016 18:55:31 +0000
Committer: Thomas Gleixner <tglx@linutronix.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@canonical.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1456512931-3388-1-git-send-email-colin.king@canonical.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.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;
}
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