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    Subject[PATCH 3.16 070/157] xen: Prevent buffer overflow in privcmd ioctl
    3.16.72-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Dan Carpenter <dan.carpenter@oracle.com>

    commit 42d8644bd77dd2d747e004e367cb0c895a606f39 upstream.

    The "call" variable comes from the user in privcmd_ioctl_hypercall().
    It's an offset into the hypercall_page[] which has (PAGE_SIZE / 32)
    elements. We need to put an upper bound on it to prevent an out of
    bounds access.

    Fixes: 1246ae0bb992 ("xen: add variable hypercall caller")
    Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
    Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Signed-off-by: Juergen Gross <jgross@suse.com>
    [bwh: Backported to 3.16: adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    arch/x86/include/asm/xen/hypercall.h | 3 +++
    1 file changed, 3 insertions(+)

    --- a/arch/x86/include/asm/xen/hypercall.h
    +++ b/arch/x86/include/asm/xen/hypercall.h
    @@ -215,6 +215,9 @@ privcmd_call(unsigned call,
    __HYPERCALL_DECLS;
    __HYPERCALL_5ARG(a1, a2, a3, a4, a5);

    + if (call >= PAGE_SIZE / sizeof(hypercall_page[0]))
    + return -EINVAL;
    +
    stac();
    asm volatile(CALL_NOSPEC
    : __HYPERCALL_5PARAM
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