lkml.org 
[lkml]   [2022]   [Jan]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH V40 12/29] x86: Lock down IO port access when the kernel is locked down
    Hi Matthew,

    On Tue, Aug 20, 2019 at 8:20 AM Matthew Garrett
    <matthewgarrett@google.com> wrote:
    >
    > From: Matthew Garrett <mjg59@srcf.ucam.org>
    >
    > 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.
    >
    > This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
    > KDDISABIO console ioctls.
    >
    > Signed-off-by: Matthew Garrett <mjg59@google.com>
    > Signed-off-by: David Howells <dhowells@redhat.com>
    > Reviewed-by: Kees Cook <keescook@chromium.org>
    > cc: x86@kernel.org
    > Signed-off-by: James Morris <jmorris@namei.org>

    This patch breaks ioperm() usage from userspace programs with CAP_SYS_RAWIO cap.

    I wonder if it's possible to revert this commit?

    Kai-Heng

    > ---
    > arch/x86/kernel/ioport.c | 7 +++++--
    > include/linux/security.h | 1 +
    > security/lockdown/lockdown.c | 1 +
    > 3 files changed, 7 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
    > index 0fe1c8782208..61a89d3c0382 100644
    > --- a/arch/x86/kernel/ioport.c
    > +++ b/arch/x86/kernel/ioport.c
    > @@ -11,6 +11,7 @@
    > #include <linux/errno.h>
    > #include <linux/types.h>
    > #include <linux/ioport.h>
    > +#include <linux/security.h>
    > #include <linux/smp.h>
    > #include <linux/stddef.h>
    > #include <linux/slab.h>
    > @@ -31,7 +32,8 @@ long ksys_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) ||
    > + security_locked_down(LOCKDOWN_IOPORT)))
    > return -EPERM;
    >
    > /*
    > @@ -126,7 +128,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
    > return -EINVAL;
    > /* Trying to gain more privileges? */
    > if (level > old) {
    > - if (!capable(CAP_SYS_RAWIO))
    > + if (!capable(CAP_SYS_RAWIO) ||
    > + security_locked_down(LOCKDOWN_IOPORT))
    > return -EPERM;
    > }
    > regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
    > diff --git a/include/linux/security.h b/include/linux/security.h
    > index 2b763f0ee352..cd93fa5d3c6d 100644
    > --- a/include/linux/security.h
    > +++ b/include/linux/security.h
    > @@ -108,6 +108,7 @@ enum lockdown_reason {
    > LOCKDOWN_KEXEC,
    > LOCKDOWN_HIBERNATION,
    > LOCKDOWN_PCI_ACCESS,
    > + LOCKDOWN_IOPORT,
    > LOCKDOWN_INTEGRITY_MAX,
    > LOCKDOWN_CONFIDENTIALITY_MAX,
    > };
    > diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
    > index 410e90eda848..8b7d65dbb086 100644
    > --- a/security/lockdown/lockdown.c
    > +++ b/security/lockdown/lockdown.c
    > @@ -23,6 +23,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
    > [LOCKDOWN_KEXEC] = "kexec of unsigned images",
    > [LOCKDOWN_HIBERNATION] = "hibernation",
    > [LOCKDOWN_PCI_ACCESS] = "direct PCI access",
    > + [LOCKDOWN_IOPORT] = "raw io port access",
    > [LOCKDOWN_INTEGRITY_MAX] = "integrity",
    > [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
    > };
    > --
    > 2.23.0.rc1.153.gdeed80330f-goog
    >

    \
     
     \ /
      Last update: 2022-01-05 07:27    [W:3.722 / U:0.152 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site