From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user()
Date: Mon, 7 Oct 2019 03:50:46 +0100 [thread overview]
Message-ID: <20191007025046.GL26530@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAHk-=whKJfX579+2f-CHc4_YmEmwvMe_Csr0+CPfLAsSAdfDoA@mail.gmail.com>
On Sun, Oct 06, 2019 at 07:06:19PM -0700, Linus Torvalds wrote:
> On Sun, Oct 6, 2019 at 6:24 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > Ugh... I wonder if it would be better to lift STAC/CLAC out of
> > raw_copy_to_user(), rather than trying to reinvent its guts
> > in readdir.c...
>
> Yeah, I suspect that's the best option.
>
> Do something like
>
> - lift STAC/CLAC out of raw_copy_to_user
>
> - rename it to unsafe_copy_to_user
>
> - create a new raw_copy_to_user that is just unsafe_copy_to_user()
> with the STAC/CLAC around it.
>
> and the end result would actually be cleanert than what we have now
> (which duplicates that STAC/CLAC for each size case etc).
>
> And then for the "architecture doesn't have user_access_begin/end()"
> fallback case, we just do
>
> #define unsafe_copy_to_user raw_copy_to_user
Callers of raw_copy_to_user():
arch/hexagon/mm/uaccess.c:27: uncleared = raw_copy_to_user(dest, &empty_zero_page, PAGE_SIZE);
arch/hexagon/mm/uaccess.c:34: count = raw_copy_to_user(dest, &empty_zero_page, count);
arch/powerpc/kvm/book3s_64_mmu_radix.c:68: ret = raw_copy_to_user(to, from, n);
arch/s390/include/asm/uaccess.h:150: size = raw_copy_to_user(ptr, x, size);
include/asm-generic/uaccess.h:145: return unlikely(raw_copy_to_user(ptr, x, size)) ? -EFAULT : 0;
include/linux/uaccess.h:93: return raw_copy_to_user(to, from, n);
include/linux/uaccess.h:102: return raw_copy_to_user(to, from, n);
include/linux/uaccess.h:131: n = raw_copy_to_user(to, from, n);
lib/iov_iter.c:142: n = raw_copy_to_user(to, from, n);
lib/usercopy.c:28: n = raw_copy_to_user(to, from, n);
Out of those, only __copy_to_user_inatomic(), __copy_to_user(),
_copy_to_user() and iov_iter.c:copyout() can be called on
any architecture.
The last two should just do user_access_begin()/user_access_end()
instead of access_ok(). __copy_to_user_inatomic() has very few callers as well:
arch/mips/kernel/unaligned.c:1307: res = __copy_to_user_inatomic(addr, fpr, sizeof(*fpr));
drivers/gpu/drm/i915/i915_gem.c:345: unwritten = __copy_to_user_inatomic(user_data,
lib/test_kasan.c:471: unused = __copy_to_user_inatomic(usermem, kmem, size + 1);
mm/maccess.c:98: ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
So few, in fact, that I wonder if we want to keep it at all; the only
thing stopping me from "let's remove it" is that I don't understand
the i915 side of things. Where does it do an equivalent of access_ok()?
And mm/maccess.c one is __probe_kernel_write(), so presumably we don't
want stac/clac there at all...
So do we want to bother with separation between raw_copy_to_user() and
unsafe_copy_to_user()? After all, __copy_to_user() also has only few
callers, most of them in arch/*
I'll take a look into that tomorrow - half-asleep right now...
next prev parent reply other threads:[~2019-10-07 2:50 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-06 22:20 [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user() Guenter Roeck
2019-10-06 23:06 ` Linus Torvalds
2019-10-06 23:35 ` Linus Torvalds
2019-10-07 0:04 ` Guenter Roeck
2019-10-07 1:17 ` Linus Torvalds
2019-10-07 1:24 ` Al Viro
2019-10-07 2:06 ` Linus Torvalds
2019-10-07 2:50 ` Al Viro [this message]
2019-10-07 3:11 ` Linus Torvalds
2019-10-07 15:40 ` David Laight
2019-10-07 18:11 ` Linus Torvalds
2019-10-08 9:58 ` David Laight
2019-10-07 17:34 ` Al Viro
2019-10-07 18:13 ` Linus Torvalds
2019-10-07 18:22 ` Al Viro
2019-10-07 18:26 ` Linus Torvalds
2019-10-07 18:36 ` Tony Luck
2019-10-07 19:08 ` Linus Torvalds
2019-10-07 19:49 ` Tony Luck
2019-10-07 20:04 ` Linus Torvalds
2019-10-08 3:29 ` Al Viro
2019-10-08 4:09 ` Linus Torvalds
2019-10-08 4:14 ` Linus Torvalds
2019-10-08 5:02 ` Al Viro
2019-10-08 4:24 ` Linus Torvalds
2019-10-10 19:55 ` Al Viro
2019-10-10 22:12 ` Linus Torvalds
2019-10-11 0:11 ` Al Viro
2019-10-11 0:31 ` Linus Torvalds
2019-10-13 18:13 ` Al Viro
2019-10-13 18:43 ` Linus Torvalds
2019-10-13 19:10 ` Al Viro
2019-10-13 19:22 ` Linus Torvalds
2019-10-13 19:59 ` Al Viro
2019-10-13 20:20 ` Linus Torvalds
2019-10-15 3:46 ` Michael Ellerman
2019-10-15 18:08 ` Al Viro
2019-10-15 19:00 ` Linus Torvalds
2019-10-15 19:40 ` Al Viro
2019-10-15 20:18 ` Al Viro
2019-10-16 12:12 ` [RFC] change of calling conventions for arch_futex_atomic_op_inuser() Al Viro
2019-10-16 12:24 ` Thomas Gleixner
2019-10-16 20:25 ` [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user() Al Viro
2019-10-17 19:36 ` [RFC][PATCHES] drivers/scsi/sg.c uaccess cleanups/fixes Al Viro
2019-10-17 19:39 ` [RFC PATCH 1/8] sg_ioctl(): fix copyout handling Al Viro
2019-10-17 19:39 ` [RFC PATCH 2/8] sg_new_write(): replace access_ok() + __copy_from_user() with copy_from_user() Al Viro
2019-10-17 19:39 ` [RFC PATCH 3/8] sg_write(): __get_user() can fail Al Viro
2019-10-17 19:39 ` [RFC PATCH 4/8] sg_read(): simplify reading ->pack_id of userland sg_io_hdr_t Al Viro
2019-10-17 19:39 ` [RFC PATCH 5/8] sg_new_write(): don't bother with access_ok Al Viro
2019-10-17 19:39 ` [RFC PATCH 6/8] sg_read(): get rid of access_ok()/__copy_..._user() Al Viro
2019-10-17 19:39 ` [RFC PATCH 7/8] sg_write(): get rid of access_ok()/__copy_from_user()/__get_user() Al Viro
2019-10-17 19:39 ` [RFC PATCH 8/8] SG_IO: get rid of access_ok() Al Viro
2019-10-17 21:44 ` [RFC][PATCHES] drivers/scsi/sg.c uaccess cleanups/fixes Douglas Gilbert
2019-11-05 4:54 ` Martin K. Petersen
2019-11-05 5:25 ` Al Viro
2019-11-06 4:29 ` Martin K. Petersen
2019-10-18 0:27 ` [RFC] csum_and_copy_from_user() semantics Al Viro
2019-10-25 14:01 ` [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user() Thomas Gleixner
2019-10-08 4:57 ` Al Viro
2019-10-08 13:14 ` Greg KH
2019-10-08 15:29 ` Al Viro
2019-10-08 15:38 ` Greg KH
2019-10-08 17:06 ` Al Viro
2019-10-08 19:58 ` Al Viro
2019-10-08 20:16 ` Al Viro
2019-10-08 20:34 ` Al Viro
2019-10-07 2:30 ` Guenter Roeck
2019-10-07 3:12 ` Linus Torvalds
2019-10-07 0:23 ` Guenter Roeck
2019-10-07 4:04 ` Max Filippov
2019-10-07 12:16 ` Guenter Roeck
2019-10-07 19:21 ` Linus Torvalds
2019-10-07 20:29 ` Guenter Roeck
2019-10-07 23:27 ` Guenter Roeck
2019-10-08 6:28 ` Geert Uytterhoeven
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