Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode

From: Arnd Bergmann <arnd@arndb.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Ingo Molnar" <mingo@kernel.org>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Greg KH" <greg@kroah.com>,
	"Thomas Garnier" <thgarnie@google.com>,
	"Martin Schwidefsky" <schwidefsky@de.ibm.com>,
	"Heiko Carstens" <heiko.carstens@de.ibm.com>,
	"Dave Hansen" <dave.hansen@intel.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"David Howells" <dhowells@redhat.com>,
	"René Nyffenegger" <mail@renenyffenegger.ch>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Pavel Tikhomirov" <ptikhomirov@virtuozzo.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"H . Peter Anvin" <hpa@zytor.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Rik van Riel" <riel@redhat.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Josh Poimboeuf" <jpoimboe@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Brian Gerst" <brgerst@gmail.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	"Christian Borntraeger" <borntraeger@de.ibm.com>,
	"Russell King" <linux@armlinux.org.uk>,
	"Will Deacon" <will.deacon@arm.com>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"James Morse" <james.morse@arm.com>,
	linux-s390 <linux-s390@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Linux API" <linux-api@vger.kernel.org>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"Kernel Hardening" <kernel-hardening@lists.openwall.com>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Peter Zijlstra" <a.p.zijlstra@chello.nl>
Subject: Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode
Date: Fri, 12 May 2017 09:43:40 +0200	[thread overview]
Message-ID: <CAK8P3a2ynRObJLn2Hh2r9_2k5+O08jErPC_UnnDmemd1jXsnkw@mail.gmail.com> (raw)
In-Reply-To: <20170512071549.GP390@ZenIV.linux.org.uk>

On Fri, May 12, 2017 at 9:15 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Fri, May 12, 2017 at 09:00:12AM +0200, Ingo Molnar wrote:
>
>> > How about trying to remove all of them?  If we could actually get rid
>> > of all of them, we could drop the arch support, and we'd get faster,
>> > simpler, shorter uaccess code throughout the kernel.
>>
>> I'm all for that!
>
> Oh, for...  Ingo, do you really want to go through all ->write() and ->read()
> instances, converting all of them to iov_iter?  Or, better yet, deal with
> the patch flood from Nick Krause sock puppet brigade?

How realistic and how useful would it be to first completely eliminate
the ones that are in loadable modules and then wrapping the definition
in #ifndef MODULE (or even make it an extern function)?

This should be a fairly complete list of the modular users:

drivers/block/drbd/drbd_main.c: set_fs(KERNEL_DS);
drivers/input/serio/hp_sdc.c:   set_fs(KERNEL_DS);
drivers/media/v4l2-core/v4l2-compat-ioctl32.c:          set_fs(KERNEL_DS);
drivers/misc/lkdtm_bugs.c:      set_fs(KERNEL_DS);
drivers/s390/crypto/pkey_api.c: set_fs(KERNEL_DS);
drivers/staging/comedi/drivers/serial2002.c:    set_fs(KERNEL_DS);
drivers/staging/lustre/lnet/libcfs/tracefile.c: set_fs(get_ds());
drivers/staging/media/atomisp/pci/atomisp2/atomisp_compat_ioctl32.c:
 set_fs(KERNEL_DS);
drivers/staging/rtl8723bs/os_dep/osdep_service.c:               oldfs
= get_fs(); set_fs(get_ds());
drivers/usb/gadget/function/f_mass_storage.c:   set_fs(get_ds());
drivers/usb/gadget/function/u_uac1.c:   set_fs(KERNEL_DS);
drivers/vhost/vhost.c:  set_fs(USER_DS);
drivers/video/fbdev/core/fbmem.c:       set_fs(KERNEL_DS);
drivers/video/fbdev/hpfb.c:     set_fs(KERNEL_DS);
fs/autofs4/waitq.c:     set_fs(KERNEL_DS);
fs/binfmt_aout.c:       set_fs(KERNEL_DS);
fs/binfmt_elf.c:                set_fs(USER_DS);
fs/binfmt_elf_fdpic.c:  set_fs(KERNEL_DS);
fs/btrfs/send.c:        set_fs(KERNEL_DS);
fs/ext4/ioctl.c:                set_fs(KERNEL_DS);
fs/nfsd/vfs.c:  set_fs(KERNEL_DS);
net/9p/trans_fd.c:      set_fs(get_ds());
net/ipv6/addrconf.c:                    set_fs(KERNEL_DS);
net/ipv6/exthdrs.c:     set_fs(KERNEL_DS);
net/sunrpc/svcsock.c:   oldfs = get_fs(); set_fs(KERNEL_DS);
sound/core/oss/pcm_oss.c:       set_fs(get_ds());
sound/core/pcm_native.c:        set_fs(get_ds());
sound/drivers/opl3/opl3_oss.c:  set_fs(get_ds());
sound/oss/dmabuf.c:     set_fs(get_ds());
sound/oss/swarm_cs4297a.c:                set_fs(KERNEL_DS);
sound/pci/emu10k1/emufx.c:      set_fs(get_ds());
sound/pci/hda/hda_codec.c:              set_fs(get_ds());

     Arnd