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    Subject[PATCH 3.19.y-ckt 144/196] x86/mpx: Fix off-by-one comparison with nr_registers
    Date
    3.19.8-ckt16 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

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

    commit 9bf148cb0812595bfdf5100bd2c07e9bec9c6ef5 upstream.

    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>
    Link: http://lkml.kernel.org/r/1456512931-3388-1-git-send-email-colin.king@canonical.com
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Kamal Mostafa <kamal@canonical.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 feda8ca..0b0382a 100644
    --- a/arch/x86/mm/mpx.c
    +++ b/arch/x86/mm/mpx.c
    @@ -142,7 +142,7 @@ 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
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