1. 17 Aug, 2017 5 commits
    • Boqun Feng's avatar
      locking/lockdep: Explicitly initialize wq_barrier::done::map · 52fa5bc5
      Boqun Feng authored
      With the new lockdep crossrelease feature, which checks completions usage,
      a false positive is reported in the workqueue code:
      > Worker A : acquired of wfc.work -> wait for cpu_hotplug_lock to be released
      > Task   B : acquired of cpu_hotplug_lock -> wait for lock#3 to be released
      > Task   C : acquired of lock#3 -> wait for completion of barr->done
      > (Task C is in lru_add_drain_all_cpuslocked())
      > Worker D : wait for wfc.work to be released -> will complete barr->done
      Such a dead lock can not happen because Task C's barr->done and Worker D's
      barr->done can not be the same instance.
      The reason of this false positive is we initialize all wq_barrier::done
      at insert_wq_barrier() via init_completion(), which makes them belong to
      the same lock class, therefore, impossible circles are reported.
      To fix this, explicitly initialize the lockdep map for wq_barrier::done
      in insert_wq_barrier(), so that the lock class key of wq_barrier::done
      is a subkey of the corresponding work_struct, as a result we won't build
      a dependency between a wq_barrier with a unrelated work, and we can
      differ wq barriers based on the related works, so the false positive
      above is avoided.
      Also define the empty lockdep_init_map_crosslock() for !CROSSRELEASE
      to make the code simple and away from unnecessary #ifdefs.
      Reported-by: default avatarIngo Molnar <mingo@kernel.org>
      Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
      Cc: Byungchul Park <byungchul.park@lge.com>
      Cc: Lai Jiangshan <jiangshanlai@gmail.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/20170817094622.12915-1-boqun.feng@gmail.com
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    • Byungchul Park's avatar
      locking/lockdep: Rename CONFIG_LOCKDEP_COMPLETE to CONFIG_LOCKDEP_COMPLETIONS · ea3f2c0f
      Byungchul Park authored
      'complete' is an adjective and LOCKDEP_COMPLETE sounds like 'lockdep is complete',
      so pick a better name that uses a noun.
      Signed-off-by: default avatarByungchul Park <byungchul.park@lge.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: kernel-team@lge.com
      Link: http://lkml.kernel.org/r/1502960261-16206-3-git-send-email-byungchul.park@lge.com
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    • Byungchul Park's avatar
      locking/lockdep: Reword title of LOCKDEP_CROSSRELEASE config · 0f0a2226
      Byungchul Park authored
      Lockdep doesn't have to be made to work with crossrelease and just works
      with them. Reword the title so that what the option does is clear.
      Signed-off-by: default avatarByungchul Park <byungchul.park@lge.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: kernel-team@lge.com
      Link: http://lkml.kernel.org/r/1502960261-16206-2-git-send-email-byungchul.park@lge.com
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    • Byungchul Park's avatar
      locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE part of CONFIG_PROVE_LOCKING · d0541b0f
      Byungchul Park authored
      options. It makes little sense to enable them when PROVE_LOCKING is disabled.
      Make them non-interative options and part of PROVE_LOCKING to simplify the UI.
      Signed-off-by: default avatarByungchul Park <byungchul.park@lge.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: kernel-team@lge.com
      Link: http://lkml.kernel.org/r/1502960261-16206-1-git-send-email-byungchul.park@lge.com
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    • Kees Cook's avatar
      locking/refcounts, x86/asm: Implement fast refcount overflow protection · 7a46ec0e
      Kees Cook authored
      This implements refcount_t overflow protection on x86 without a noticeable
      performance impact, though without the fuller checking of REFCOUNT_FULL.
      This is done by duplicating the existing atomic_t refcount implementation
      but with normally a single instruction added to detect if the refcount
      has gone negative (e.g. wrapped past INT_MAX or below zero). When detected,
      the handler saturates the refcount_t to INT_MIN / 2. With this overflow
      protection, the erroneous reference release that would follow a wrap back
      to zero is blocked from happening, avoiding the class of refcount-overflow
      use-after-free vulnerabilities entirely.
      Only the overflow case of refcounting can be perfectly protected, since
      it can be detected and stopped before the reference is freed and left to
      be abused by an attacker. There isn't a way to block early decrements,
      and while REFCOUNT_FULL stops increment-from-zero cases (which would
      be the state _after_ an early decrement and stops potential double-free
      conditions), this fast implementation does not, since it would require
      the more expensive cmpxchg loops. Since the overflow case is much more
      common (e.g. missing a "put" during an error path), this protection
      provides real-world protection. For example, the two public refcount
      overflow use-after-free exploits published in 2016 would have been
      rendered unexploitable:
      This implementation does, however, notice an unchecked decrement to zero
      (i.e. caller used refcount_dec() instead of refcount_dec_and_test() and it
      resulted in a zero). Decrements under zero are noticed (since they will
      have resulted in a negative value), though this only indicates that a
      use-after-free may have already happened. Such notifications are likely
      avoidable by an attacker that has already exploited a use-after-free
      vulnerability, but it's better to have them reported than allow such
      conditions to remain universally silent.
      On first overflow detection, the refcount value is reset to INT_MIN / 2
      (which serves as a saturation value) and a report and stack trace are
      produced. When operations detect only negative value results (such as
      changing an already saturated value), saturation still happens but no
      notification is performed (since the value was already saturated).
      On the matter of races, since the entire range beyond INT_MAX but before
      0 is negative, every operation at INT_MIN / 2 will trap, leaving no
      overflow-only race condition.
      As for performance, this implementation adds a single "js" instruction
      to the regular execution flow of a copy of the standard atomic_t refcount
      operations. (The non-"and_test" refcount_dec() function, which is uncommon
      in regular refcount design patterns, has an additional "jz" instruction
      to detect reaching exactly zero.) Since this is a forward jump, it is by
      default the non-predicted path, which will be reinforced by dynamic branch
      prediction. The result is this protection having virtually no measurable
      change in performance over standard atomic_t operations. The error path,
      located in .text.unlikely, saves the refcount location and then uses UD0
      to fire a refcount exception handler, which resets the refcount, handles
      reporting, and returns to regular execution. This keeps the changes to
      .text size minimal, avoiding return jumps and open-coded calls to the
      error reporting routine.
      Example assembly comparison:
      refcount_inc() before:
        ffffffff81546149:       f0 ff 45 f4             lock incl -0xc(%rbp)
      refcount_inc() after:
        ffffffff81546149:       f0 ff 45 f4             lock incl -0xc(%rbp)
        ffffffff8154614d:       0f 88 80 d5 17 00       js     ffffffff816c36d3
        ffffffff816c36d3:       48 8d 4d f4             lea    -0xc(%rbp),%rcx
        ffffffff816c36d7:       0f ff                   (bad)
      These are the cycle counts comparing a loop of refcount_inc() from 1
      to INT_MAX and back down to 0 (via refcount_dec_and_test()), between
      unprotected refcount_t (atomic_t), fully protected REFCOUNT_FULL
      (refcount_t-full), and this overflow-protected refcount (refcount_t-fast):
        2147483646 refcount_inc()s and 2147483647 refcount_dec_and_test()s:
      		    cycles		protections
        atomic_t           82249267387	none
        refcount_t-fast    82211446892	overflow, untested dec-to-zero
        refcount_t-full   144814735193	overflow, untested dec-to-zero, inc-from-zero
      This code is a modified version of the x86 PAX_REFCOUNT atomic_t
      overflow defense from the last public patch of PaX/grsecurity, based
      on my understanding of the code. Changes or omissions from the original
      code are mine and don't reflect the original grsecurity/PaX code. Thanks
      to PaX Team for various suggestions for improvement for repurposing this
      code to be a refcount-only protection.
      Signed-off-by: default avatarKees Cook <keescook@chromium.org>
      Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Alexey Dobriyan <adobriyan@gmail.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Davidlohr Bueso <dave@stgolabs.net>
      Cc: Elena Reshetova <elena.reshetova@intel.com>
      Cc: Eric Biggers <ebiggers3@gmail.com>
      Cc: Eric W. Biederman <ebiederm@xmission.com>
      Cc: Greg KH <gregkh@linuxfoundation.org>
      Cc: Hans Liljestrand <ishkamiel@gmail.com>
      Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
      Cc: Jann Horn <jannh@google.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Manfred Spraul <manfred@colorfullife.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Serge E. Hallyn <serge@hallyn.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: arozansk@redhat.com
      Cc: axboe@kernel.dk
      Cc: kernel-hardening@lists.openwall.com
      Cc: linux-arch <linux-arch@vger.kernel.org>
      Link: http://lkml.kernel.org/r/20170815161924.GA133115@beast
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
  2. 14 Aug, 2017 2 commits
  3. 11 Aug, 2017 3 commits
    • Peter Zijlstra's avatar
      mm, locking: Fix up flush_tlb_pending() related merge in do_huge_pmd_numa_page() · ccde85ba
      Peter Zijlstra authored
      Merge commit:
        040cca3a ("Merge branch 'linus' into locking/core, to resolve conflicts")
      overlooked the fact that do_huge_pmd_numa_page() now does two TLB
      flushes. Commit:
        8b1b436d ("mm, locking: Rework {set,clear,mm}_tlb_flush_pending()")
      and commit:
       ("Revert "mm: numa: defer TLB flush for THP migration as long as possible"")
      Both moved the TLB flush around but slightly different, the end result
      being that what was one became two.
      Clean this up.
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Russell King <linux@armlinux.org.uk>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Vineet Gupta <vgupta@synopsys.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    • Ingo Molnar's avatar
      Merge branch 'linus' into locking/core, to resolve conflicts · 040cca3a
      Ingo Molnar authored
      I removed the smp_mb__before_spinlock() like the following commit does:
       ("mm, locking: Rework {set,clear,mm}_tlb_flush_pending()")
      and fixed up the affected commits.
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    • Linus Torvalds's avatar
      Merge tag 'drm-fixes-for-v4.13-rc5' of git://people.freedesktop.org/~airlied/linux · b2dbdf2c
      Linus Torvalds authored
      Pull drm fixes from Dave Airlie:
       "Nothing too earth shattering here, it just seems like lots of little
        things all over the place.
        msm has probably the larger amount of changes, but they all seem fine,
        otherwise, some rockchip, i915, etnaviv and exynos fixes, along with
        one nouveau regression fix for some older GPUs"
      * tag 'drm-fixes-for-v4.13-rc5' of git://people.freedesktop.org/~airlied/linux: (35 commits)
        drm/nouveau/disp/nv04: avoid creation of output paths
        drm: make DRM_STM default n
        drm/exynos: forbid creating framebuffers from too small GEM buffers
        drm/etnaviv: Fix off-by-one error in reloc checking
        drm/i915: fix backlight invert for non-zero minimum brightness
        drm/i915/shrinker: Wrap need_resched() inside preempt-disable
        drm/i915/perf: fix flex eu registers programming
        drm/i915: Fix out-of-bounds array access in bdw_load_gamma_lut
        drm/i915/gvt: Change the max length of mmio_reg_rw from 4 to 8
        drm/i915/gvt: Initialize MMIO Block with HW state
        drm/rockchip: vop: report error when check resource error
        drm/rockchip: vop: round_up pitches to word align
        drm/rockchip: vop: fix NV12 video display error
        drm/rockchip: vop: fix iommu page fault when resume
        drm/i915/gvt: clean workload queue if error happened
        drm/i915/gvt: change resetting to resetting_eng
        drm/msm: gpu: don't abuse dma_alloc for non-DMA allocations
        drm/msm: gpu: call qcom_mdt interfaces only for ARCH_QCOM
        drm/msm/adreno: Prevent unclocked access when retrieving timestamps
        drm/msm: Remove __user from __u64 data types
  4. 10 Aug, 2017 30 commits