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  1. 10 Sep, 2017 4 commits
  3. 09 Sep, 2017 15 commits
  5. 07 Sep, 2017 6 commits
    • Andy Lutomirski's avatar
      x86/mm: Document how CR4.PCIDE restore works · 1c9fe440
      Andy Lutomirski authored 
      

While debugging a problem, I thought that using
cr4_set_bits_and_update_boot() to restore CR4.PCIDE would be
helpful.  It turns out to be counterproductive.

Add a comment documenting how this works.
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1c9fe440
    • Andy Lutomirski's avatar
      x86/mm: Reinitialize TLB state on hotplug and resume · 72c0098d
      Andy Lutomirski authored 
      

When Linux brings a CPU down and back up, it switches to init_mm and then
loads swapper_pg_dir into CR3.  With PCID enabled, this has the side effect
of masking off the ASID bits in CR3.

This can result in some confusion in the TLB handling code.  If we
bring a CPU down and back up with any ASID other than 0, we end up
with the wrong ASID active on the CPU after resume.  This could
cause our internal state to become corrupt, although major
corruption is unlikely because init_mm doesn't have any user pages.
More obviously, if CONFIG_DEBUG_VM=y, we'll trip over an assertion
in the next context switch.  The result of *that* is a failure to
resume from suspend with probability 1 - 1/6^(cpus-1).

Fix it by reinitializing cpu_tlbstate on resume and CPU bringup.
Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Reported-by: default avatarJiri Kosina <jikos@kernel.org>
Fixes: 10af6235

 ("x86/mm: Implement PCID based optimization: try to preserve old TLB entries using PCID")
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      72c0098d
    • Rik van Riel's avatar
      mm,fork: introduce MADV_WIPEONFORK · d2cd9ede
      Rik van Riel authored 
      Introduce MADV_WIPEONFORK semantics, which result in a VMA being empty
in the child process after fork.  This differs from MADV_DONTFORK in one
important way.

If a child process accesses memory that was MADV_WIPEONFORK, it will get
zeroes.  The address ranges are still valid, they are just empty.

If a child process accesses memory that was MADV_DONTFORK, it will get a
segmentation fault, since those address ranges are no longer valid in
the child after fork.

Since MADV_DONTFORK also seems to be used to allow very large programs
to fork in systems with strict memory overcommit restrictions, changing
the semantics of MADV_DONTFORK might break existing programs.

MADV_WIPEONFORK only works on private, anonymous VMAs.

The use case is libraries that store or cache information, and want to
know that they need to regenerate it in the child process after fork.

Examples of this would be:
 - systemd/pulseaudio API checks (fail after fork) (replacing a getpid
   check, which is too slow without a PID cache)
 - PKCS#11 API reinitialization check (mandated by specification)
 - glibc's upcoming PRNG (reseed after fork)
 - OpenSSL PRNG (reseed after fork)

The security benefits of a forking server having a re-inialized PRNG in
every child process are pretty obvious.  However, due to libraries
having all kinds of internal state, and programs getting compiled with
many different versions of each library, it is unreasonable to expect
calling programs to re-initialize everything manually after fork.

A further complication is the proliferation of clone flags, programs
bypassing glibc's functions to call clone directly, and programs calling
unshare, causing the glibc pthread_atfork hook to not get called.

It would be better to have the kernel take care of this automatically.

The patch also adds MADV_KEEPONFORK, to undo the effects of a prior
MADV_WIPEONFORK.

This is similar to the OpenBSD minherit syscall with MAP_INHERIT_ZERO:

    https://man.openbsd.org/minherit.2

[akpm@linux-foundation.org: numerically order arch/parisc/include/uapi/asm/mman.h #defines]
Link: http://lkml.kernel.org/r/20170811212829.29186-3-riel@redhat.com

Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Reported-by: default avatarFlorian Weimer <fweimer@redhat.com>
Reported-by: default avatarColm MacCártaigh <colm@allcosts.net>
Reviewed-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d2cd9ede
    • Rik van Riel's avatar
      x86,mpx: make mpx depend on x86-64 to free up VMA flag · df3735c5
      Rik van Riel authored 
      Patch series "mm,fork,security: introduce MADV_WIPEONFORK", v4.

If a child process accesses memory that was MADV_WIPEONFORK, it will get
zeroes.  The address ranges are still valid, they are just empty.

If a child process accesses memory that was MADV_DONTFORK, it will get a
segmentation fault, since those address ranges are no longer valid in
the child after fork.

Since MADV_DONTFORK also seems to be used to allow very large programs
to fork in systems with strict memory overcommit restrictions, changing
the semantics of MADV_DONTFORK might break existing programs.

The use case is libraries that store or cache information, and want to
know that they need to regenerate it in the child process after fork.

Examples of this would be:
 - systemd/pulseaudio API checks (fail after fork) (replacing a getpid
   check, which is too slow without a PID cache)
 - PKCS#11 API reinitialization check (mandated by specification)
 - glibc's upcoming PRNG (reseed after fork)
 - OpenSSL PRNG (reseed after fork)

The security benefits of a forking server having a re-inialized PRNG in
every child process are pretty obvious.  However, due to libraries
having all kinds of internal state, and programs getting compiled with
many different versions of each library, it is unreasonable to expect
calling programs to re-initialize everything manually after fork.

A further complication is the proliferation of clone flags, programs
bypassing glibc's functions to call clone directly, and programs calling
unshare, causing the glibc pthread_atfork hook to not get called.

It would be better to have the kernel take care of this automatically.

The patchset also adds MADV_KEEPONFORK, to undo the effects of a prior
MADV_WIPEONFORK.

This is similar to the OpenBSD minherit syscall with MAP_INHERIT_ZERO:

    https://man.openbsd.org/minherit.2

This patch (of 2):

MPX only seems to be available on 64 bit CPUs, starting with Skylake and
Goldmont.  Move VM_MPX into the 64 bit only portion of vma->vm_flags, in
order to free up a VMA flag.

Link: http://lkml.kernel.org/r/20170811212829.29186-2-riel@redhat.com

Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarDave Hansen <dave.hansen@intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Colm MacCártaigh <colm@allcosts.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      df3735c5
    • Mike Kravetz's avatar
      mm: arch: consolidate mmap hugetlb size encodings · aafd4562
      Mike Kravetz authored 
      A non-default huge page size can be encoded in the flags argument of the
mmap system call.  The definitions for these encodings are in arch
specific header files.  However, all architectures use the same values.

Consolidate all the definitions in the primary user header file
(uapi/linux/mman.h).  Include definitions for all known huge page sizes.
Use the generic encoding definitions in hugetlb_encode.h as the basis
for these definitions.

Link: http://lkml.kernel.org/r/1501527386-10736-3-git-send-email-mike.kravetz@oracle.com

Signed-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      aafd4562
    • Dou Liyang's avatar
      metag/numa: remove the unused parent_node() macro · f0cd3406
      Dou Liyang authored 
      Commit a7be6e5a ("mm: drop useless local parameters of
__register_one_node()") removes the last user of parent_node().

The parent_node() macro in METAG architecture is unnecessary.

Remove it for cleanup.

Link: http://lkml.kernel.org/r/1501076076-1974-4-git-send-email-douly.fnst@cn.fujitsu.com

Signed-off-by: default avatarDou Liyang <douly.fnst@cn.fujitsu.com>
Reported-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Cc: James Hogan <james.hogan@imgtec.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f0cd3406
  7. 05 Sep, 2017 2 commits
  9. 04 Sep, 2017 13 commits

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