linux/arch/sparc
Linus Torvalds f6f3732162 Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths"
This reverts commits 5c9d2d5c26, c7da82b894, and e7fe7b5cae.

We'll probably need to revisit this, but basically we should not
complicate the get_user_pages_fast() case, and checking the actual page
table protection key bits will require more care anyway, since the
protection keys depend on the exact state of the VM in question.

Particularly when doing a "remote" page lookup (ie in somebody elses VM,
not your own), you need to be much more careful than this was.  Dave
Hansen says:

 "So, the underlying bug here is that we now a get_user_pages_remote()
  and then go ahead and do the p*_access_permitted() checks against the
  current PKRU. This was introduced recently with the addition of the
  new p??_access_permitted() calls.

  We have checks in the VMA path for the "remote" gups and we avoid
  consulting PKRU for them. This got missed in the pkeys selftests
  because I did a ptrace read, but not a *write*. I also didn't
  explicitly test it against something where a COW needed to be done"

It's also not entirely clear that it makes sense to check the protection
key bits at this level at all.  But one possible eventual solution is to
make the get_user_pages_fast() case just abort if it sees protection key
bits set, which makes us fall back to the regular get_user_pages() case,
which then has a vma and can do the check there if we want to.

We'll see.

Somewhat related to this all: what we _do_ want to do some day is to
check the PAGE_USER bit - it should obviously always be set for user
pages, but it would be a good check to have back.  Because we have no
generic way to test for it, we lost it as part of moving over from the
architecture-specific x86 GUP implementation to the generic one in
commit e585513b76 ("x86/mm/gup: Switch GUP to the generic
get_user_page_fast() implementation").

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-12-15 18:53:22 -08:00
..
boot License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
configs sparc64: vcc: Enable VCC module in linux 2017-08-15 21:33:50 -07:00
crypto License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
include bpf: correct broken uapi for BPF_PROG_TYPE_PERF_EVENT program type 2017-12-05 15:02:40 +01:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2017-11-17 20:21:44 -08:00
lib sparc64: Fix boot on T4 and later. 2017-11-29 15:09:29 -05:00
math-emu License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mm Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths" 2017-12-15 18:53:22 -08:00
net License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
oprofile
power License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
prom License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
vdso vDSO for sparc 2017-11-15 14:21:03 +09:00
Kbuild vDSO for sparc 2017-11-15 14:21:03 +09:00
Kconfig Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2017-11-17 20:21:44 -08:00
Kconfig.debug License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2017-11-17 20:21:44 -08:00