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    Subject[PATCH V2 03/10] x86: Lock down IO port access in secure boot environments
    Date
    IO port access would permit users to gain access to PCI configuration
    registers, which in turn (on a lot of hardware) give access to MMIO register
    space. This would potentially permit root to trigger arbitrary DMA, so lock
    it down by default.

    Signed-off-by: Matthew Garrett <mjg@redhat.com>
    ---
    arch/x86/kernel/ioport.c | 4 ++--
    drivers/char/mem.c | 3 +++
    2 files changed, 5 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
    index 8c96897..a2578c4 100644
    --- a/arch/x86/kernel/ioport.c
    +++ b/arch/x86/kernel/ioport.c
    @@ -28,7 +28,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)

    if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
    return -EINVAL;
    - if (turn_on && !capable(CAP_SYS_RAWIO))
    + if (turn_on && (!capable(CAP_SYS_RAWIO) || !capable(CAP_COMPROMISE_KERNEL)))
    return -EPERM;

    /*
    @@ -102,7 +102,7 @@ long sys_iopl(unsigned int level, struct pt_regs *regs)
    return -EINVAL;
    /* Trying to gain more privileges? */
    if (level > old) {
    - if (!capable(CAP_SYS_RAWIO))
    + if (!capable(CAP_SYS_RAWIO) || !capable(CAP_COMPROMISE_KERNEL))
    return -EPERM;
    }
    regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
    diff --git a/drivers/char/mem.c b/drivers/char/mem.c
    index e5eedfa2..1e0a660 100644
    --- a/drivers/char/mem.c
    +++ b/drivers/char/mem.c
    @@ -597,6 +597,9 @@ static ssize_t write_port(struct file *file, const char __user *buf,
    unsigned long i = *ppos;
    const char __user * tmp = buf;

    + if (!capable(CAP_COMPROMISE_KERNEL))
    + return -EPERM;
    +
    if (!access_ok(VERIFY_READ, buf, count))
    return -EFAULT;
    while (count-- > 0 && i < 65536) {
    --
    1.7.11.4


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