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  1. Mar 13, 2019
  2. Mar 12, 2019
  3. Mar 08, 2019
  4. Mar 06, 2019
    • Changbin Du's avatar
      mm/page_owner: move config option to mm/Kconfig.debug · 8aa49762
      Changbin Du authored
      Move the PAGE_OWNER option from submenu "Compile-time checks and
      compiler options" to dedicated submenu "Memory Debugging".
      
      Link: http://lkml.kernel.org/r/20190120024254.6270-1-changbin.du@gmail.com
      
      
      Signed-off-by: default avatarChangbin Du <changbin.du@gmail.com>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Randy Dunlap <rdunlap@infradead.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      8aa49762
    • Uladzislau Rezki (Sony)'s avatar
      vmalloc: add test driver to analyse vmalloc allocator · 3f21a6b7
      Uladzislau Rezki (Sony) authored
      This adds a new kernel module for analysis of vmalloc allocator.  It is
      only enabled as a module.  There are two main reasons this module should
      be used for: performance evaluation and stressing of vmalloc subsystem.
      
      It consists of several test cases.  As of now there are 8.  The module
      has five parameters we can specify to change its the behaviour.
      
      1) run_test_mask - set of tests to be run
      
      id: 1,   name: fix_size_alloc_test
      id: 2,   name: full_fit_alloc_test
      id: 4,   name: long_busy_list_alloc_test
      id: 8,   name: random_size_alloc_test
      id: 16,  name: fix_align_alloc_test
      id: 32,  name: random_size_align_alloc_test
      id: 64,  name: align_shift_alloc_test
      id: 128, name: pcpu_alloc_test
      
      By default all tests are in run test mask.  If you want to select some
      specific tests it is possible to pass the mask.  For example for first,
      second and fourth tests we go 11 value.
      
      2) test_repeat_count - how many times each test should be repeated
      By default it is one time per test. It is possible to pass any number.
      As high the value is the test duration gets increased.
      
      3) test_loop_count - internal test loop counter. By default it is set
      to 1000000.
      
      4) single_cpu_test - use one CPU to run the tests
      By default this parameter is set to false. It means that all online
      CPUs execute tests. By setting it to 1, the tests are executed by
      first online CPU only.
      
      5) sequential_test_order - run tests in sequential order
      By default this parameter is set to false. It means that before running
      tests the order is shuffled. It is possible to make it sequential, just
      set it to 1.
      
      Performance analysis:
      In order to evaluate performance of vmalloc allocations, usually it
      makes sense to use only one CPU that runs tests, use sequential order,
      number of repeat tests can be different as well as set of test mask.
      
      For example if we want to run all tests, to use one CPU and repeat each
      test 3 times. Insert the module passing following parameters:
      
      single_cpu_test=1 sequential_test_order=1 test_repeat_count=3
      
      with following output:
      
      <snip>
      Summary: fix_size_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 901177 usec
      Summary: full_fit_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 1039341 usec
      Summary: long_busy_list_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 11775763 usec
      Summary: random_size_alloc_test passed 3: failed: 0 repeat: 3 loops: 1000000 avg: 6081992 usec
      Summary: fix_align_alloc_test passed: 3 failed: 0 repeat: 3, loops: 1000000 avg: 2003712 usec
      Summary: random_size_align_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 2895689 usec
      Summary: align_shift_alloc_test passed: 0 failed: 3 repeat: 3 loops: 1000000 avg: 573 usec
      Summary: pcpu_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 95802 usec
      All test took CPU0=192945605995 cycles
      <snip>
      
      The align_shift_alloc_test is expected to be failed.
      
      Stressing:
      In order to stress the vmalloc subsystem we run all available test cases
      on all available CPUs simultaneously. In order to prevent constant behaviour
      pattern, the test cases array is shuffled by default to randomize the order
      of test execution.
      
      For example if we want to run all tests(default), use all online CPUs(default)
      with shuffled order(default) and to repeat each test 30 times. The command
      would be like:
      
      modprobe vmalloc_test test_repeat_count=30
      
      Expected results are the system is alive, there are no any BUG_ONs or Kernel
      Panics the tests are completed, no memory leaks.
      
      [urezki@gmail.com: fix 32-bit builds]
        Link: http://lkml.kernel.org/r/20190106214839.ffvjvmrn52uqog7k@pc636
      [urezki@gmail.com: make CONFIG_TEST_VMALLOC depend on CONFIG_MMU]
        Link: http://lkml.kernel.org/r/20190219085441.s6bg2gpy4esny5vw@pc636
      Link: http://lkml.kernel.org/r/20190103142108.20744-3-urezki@gmail.com
      
      
      Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Matthew Wilcox <willy@infradead.org>
      Cc: Michal Hocko <mhocko@suse.com>
      Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
      Cc: Shuah Khan <shuah@kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3f21a6b7
    • Anshuman Khandual's avatar
      mm: replace all open encodings for NUMA_NO_NODE · 98fa15f3
      Anshuman Khandual authored
      Patch series "Replace all open encodings for NUMA_NO_NODE", v3.
      
      All these places for replacement were found by running the following
      grep patterns on the entire kernel code.  Please let me know if this
      might have missed some instances.  This might also have replaced some
      false positives.  I will appreciate suggestions, inputs and review.
      
      1. git grep "nid == -1"
      2. git grep "node == -1"
      3. git grep "nid = -1"
      4. git grep "node = -1"
      
      This patch (of 2):
      
      At present there are multiple places where invalid node number is
      encoded as -1.  Even though implicitly understood it is always better to
      have macros in there.  Replace these open encodings for an invalid node
      number with the global macro NUMA_NO_NODE.  This helps remove NUMA
      related assumptions like 'invalid node' from various places redirecting
      them to a common definition.
      
      Link: http://lkml.kernel.org/r/1545127933-10711-2-git-send-email-anshuman.khandual@arm.com
      
      
      Signed-off-by: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
      Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
      Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>	[ixgbe]
      Acked-by: Jens Axboe <axboe@kernel.dk>			[mtip32xx]
      Acked-by: Vinod Koul <vkoul@kernel.org>			[dmaengine.c]
      Acked-by: Michael Ellerman <mpe@ellerman.id.au>		[powerpc]
      Acked-by: Doug Ledford <dledford@redhat.com>		[drivers/infiniband]
      Cc: Joseph Qi <jiangqi903@gmail.com>
      Cc: Hans Verkuil <hverkuil@xs4all.nl>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      98fa15f3
    • Andrey Ryabinin's avatar
      kasan: remove use after scope bugs detection. · 7771bdbb
      Andrey Ryabinin authored
      Use after scope bugs detector seems to be almost entirely useless for
      the linux kernel.  It exists over two years, but I've seen only one
      valid bug so far [1].  And the bug was fixed before it has been
      reported.  There were some other use-after-scope reports, but they were
      false-positives due to different reasons like incompatibility with
      structleak plugin.
      
      This feature significantly increases stack usage, especially with GCC <
      9 version, and causes a 32K stack overflow.  It probably adds
      performance penalty too.
      
      Given all that, let's remove use-after-scope detector entirely.
      
      While preparing this patch I've noticed that we mistakenly enable
      use-after-scope detection for clang compiler regardless of
      CONFIG_KASAN_EXTRA setting.  This is also fixed now.
      
      [1] http://lkml.kernel.org/r/<20171129052106.rhgbjhhis53hkgfn@wfg-t540p.sh.intel.com>
      
      Link: http://lkml.kernel.org/r/20190111185842.13978-1-aryabinin@virtuozzo.com
      
      
      Signed-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Acked-by: Will Deacon <will.deacon@arm.com>		[arm64]
      Cc: Qian Cai <cai@lca.pw>
      Cc: Alexander Potapenko <glider@google.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7771bdbb
  5. Mar 04, 2019
    • Kees Cook's avatar
      lib: Introduce test_stackinit module · 50ceaa95
      Kees Cook authored
      
      Adds test for stack initialization coverage. We have several build options
      that control the level of stack variable initialization. This test lets us
      visualize which options cover which cases, and provide tests for some of
      the pathological padding conditions the compiler will sometimes fail to
      initialize.
      
      All options pass the explicit initialization cases and the partial
      initializers (even with padding):
      
      test_stackinit: u8_zero ok
      test_stackinit: u16_zero ok
      test_stackinit: u32_zero ok
      test_stackinit: u64_zero ok
      test_stackinit: char_array_zero ok
      test_stackinit: small_hole_zero ok
      test_stackinit: big_hole_zero ok
      test_stackinit: trailing_hole_zero ok
      test_stackinit: packed_zero ok
      test_stackinit: small_hole_dynamic_partial ok
      test_stackinit: big_hole_dynamic_partial ok
      test_stackinit: trailing_hole_dynamic_partial ok
      test_stackinit: packed_dynamic_partial ok
      test_stackinit: small_hole_static_partial ok
      test_stackinit: big_hole_static_partial ok
      test_stackinit: trailing_hole_static_partial ok
      test_stackinit: packed_static_partial ok
      test_stackinit: packed_static_all ok
      test_stackinit: packed_dynamic_all ok
      test_stackinit: packed_runtime_all ok
      
      The results of the other tests (which contain no explicit initialization),
      change based on the build's configured compiler instrumentation.
      
      No options:
      
      test_stackinit: small_hole_static_all FAIL (uninit bytes: 3)
      test_stackinit: big_hole_static_all FAIL (uninit bytes: 61)
      test_stackinit: trailing_hole_static_all FAIL (uninit bytes: 7)
      test_stackinit: small_hole_dynamic_all FAIL (uninit bytes: 3)
      test_stackinit: big_hole_dynamic_all FAIL (uninit bytes: 61)
      test_stackinit: trailing_hole_dynamic_all FAIL (uninit bytes: 7)
      test_stackinit: small_hole_runtime_partial FAIL (uninit bytes: 23)
      test_stackinit: big_hole_runtime_partial FAIL (uninit bytes: 127)
      test_stackinit: trailing_hole_runtime_partial FAIL (uninit bytes: 24)
      test_stackinit: packed_runtime_partial FAIL (uninit bytes: 24)
      test_stackinit: small_hole_runtime_all FAIL (uninit bytes: 3)
      test_stackinit: big_hole_runtime_all FAIL (uninit bytes: 61)
      test_stackinit: trailing_hole_runtime_all FAIL (uninit bytes: 7)
      test_stackinit: u8_none FAIL (uninit bytes: 1)
      test_stackinit: u16_none FAIL (uninit bytes: 2)
      test_stackinit: u32_none FAIL (uninit bytes: 4)
      test_stackinit: u64_none FAIL (uninit bytes: 8)
      test_stackinit: char_array_none FAIL (uninit bytes: 16)
      test_stackinit: switch_1_none FAIL (uninit bytes: 8)
      test_stackinit: switch_2_none FAIL (uninit bytes: 8)
      test_stackinit: small_hole_none FAIL (uninit bytes: 24)
      test_stackinit: big_hole_none FAIL (uninit bytes: 128)
      test_stackinit: trailing_hole_none FAIL (uninit bytes: 32)
      test_stackinit: packed_none FAIL (uninit bytes: 32)
      test_stackinit: user FAIL (uninit bytes: 32)
      test_stackinit: failures: 25
      
      CONFIG_GCC_PLUGIN_STRUCTLEAK_USER=y
      This only tries to initialize structs with __user markings, so
      only the difference from above is now the "user" test passes:
      
      test_stackinit: small_hole_static_all FAIL (uninit bytes: 3)
      test_stackinit: big_hole_static_all FAIL (uninit bytes: 61)
      test_stackinit: trailing_hole_static_all FAIL (uninit bytes: 7)
      test_stackinit: small_hole_dynamic_all FAIL (uninit bytes: 3)
      test_stackinit: big_hole_dynamic_all FAIL (uninit bytes: 61)
      test_stackinit: trailing_hole_dynamic_all FAIL (uninit bytes: 7)
      test_stackinit: small_hole_runtime_partial FAIL (uninit bytes: 23)
      test_stackinit: big_hole_runtime_partial FAIL (uninit bytes: 127)
      test_stackinit: trailing_hole_runtime_partial FAIL (uninit bytes: 24)
      test_stackinit: packed_runtime_partial FAIL (uninit bytes: 24)
      test_stackinit: small_hole_runtime_all FAIL (uninit bytes: 3)
      test_stackinit: big_hole_runtime_all FAIL (uninit bytes: 61)
      test_stackinit: trailing_hole_runtime_all FAIL (uninit bytes: 7)
      test_stackinit: u8_none FAIL (uninit bytes: 1)
      test_stackinit: u16_none FAIL (uninit bytes: 2)
      test_stackinit: u32_none FAIL (uninit bytes: 4)
      test_stackinit: u64_none FAIL (uninit bytes: 8)
      test_stackinit: char_array_none FAIL (uninit bytes: 16)
      test_stackinit: switch_1_none FAIL (uninit bytes: 8)
      test_stackinit: switch_2_none FAIL (uninit bytes: 8)
      test_stackinit: small_hole_none FAIL (uninit bytes: 24)
      test_stackinit: big_hole_none FAIL (uninit bytes: 128)
      test_stackinit: trailing_hole_none FAIL (uninit bytes: 32)
      test_stackinit: packed_none FAIL (uninit bytes: 32)
      test_stackinit: user ok
      test_stackinit: failures: 24
      
      CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF=y
      This initializes all structures passed by reference (scalars and strings
      remain uninitialized):
      
      test_stackinit: small_hole_static_all ok
      test_stackinit: big_hole_static_all ok
      test_stackinit: trailing_hole_static_all ok
      test_stackinit: small_hole_dynamic_all ok
      test_stackinit: big_hole_dynamic_all ok
      test_stackinit: trailing_hole_dynamic_all ok
      test_stackinit: small_hole_runtime_partial ok
      test_stackinit: big_hole_runtime_partial ok
      test_stackinit: trailing_hole_runtime_partial ok
      test_stackinit: packed_runtime_partial ok
      test_stackinit: small_hole_runtime_all ok
      test_stackinit: big_hole_runtime_all ok
      test_stackinit: trailing_hole_runtime_all ok
      test_stackinit: u8_none FAIL (uninit bytes: 1)
      test_stackinit: u16_none FAIL (uninit bytes: 2)
      test_stackinit: u32_none FAIL (uninit bytes: 4)
      test_stackinit: u64_none FAIL (uninit bytes: 8)
      test_stackinit: char_array_none FAIL (uninit bytes: 16)
      test_stackinit: switch_1_none FAIL (uninit bytes: 8)
      test_stackinit: switch_2_none FAIL (uninit bytes: 8)
      test_stackinit: small_hole_none ok
      test_stackinit: big_hole_none ok
      test_stackinit: trailing_hole_none ok
      test_stackinit: packed_none ok
      test_stackinit: user ok
      test_stackinit: failures: 7
      
      CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL=y
      This initializes all variables, so it matches above with the scalars
      and arrays included:
      
      test_stackinit: small_hole_static_all ok
      test_stackinit: big_hole_static_all ok
      test_stackinit: trailing_hole_static_all ok
      test_stackinit: small_hole_dynamic_all ok
      test_stackinit: big_hole_dynamic_all ok
      test_stackinit: trailing_hole_dynamic_all ok
      test_stackinit: small_hole_runtime_partial ok
      test_stackinit: big_hole_runtime_partial ok
      test_stackinit: trailing_hole_runtime_partial ok
      test_stackinit: packed_runtime_partial ok
      test_stackinit: small_hole_runtime_all ok
      test_stackinit: big_hole_runtime_all ok
      test_stackinit: trailing_hole_runtime_all ok
      test_stackinit: u8_none ok
      test_stackinit: u16_none ok
      test_stackinit: u32_none ok
      test_stackinit: u64_none ok
      test_stackinit: char_array_none ok
      test_stackinit: switch_1_none ok
      test_stackinit: switch_2_none ok
      test_stackinit: small_hole_none ok
      test_stackinit: big_hole_none ok
      test_stackinit: trailing_hole_none ok
      test_stackinit: packed_none ok
      test_stackinit: user ok
      test_stackinit: all tests passed!
      
      Signed-off-by: default avatarKees Cook <keescook@chromium.org>
      Reviewed-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
      50ceaa95
  6. Mar 01, 2019
    • Arnd Bergmann's avatar
      kasan: turn off asan-stack for clang-8 and earlier · 6baec880
      Arnd Bergmann authored
      Building an arm64 allmodconfig kernel with clang results in over 140
      warnings about overly large stack frames, the worst ones being:
      
        drivers/gpu/drm/panel/panel-sitronix-st7789v.c:196:12: error: stack frame size of 20224 bytes in function 'st7789v_prepare'
        drivers/video/fbdev/omap2/omapfb/displays/panel-tpo-td028ttec1.c:196:12: error: stack frame size of 13120 bytes in function 'td028ttec1_panel_enable'
        drivers/usb/host/max3421-hcd.c:1395:1: error: stack frame size of 10048 bytes in function 'max3421_spi_thread'
        drivers/net/wan/slic_ds26522.c:209:12: error: stack frame size of 9664 bytes in function 'slic_ds26522_probe'
        drivers/crypto/ccp/ccp-ops.c:2434:5: error: stack frame size of 8832 bytes in function 'ccp_run_cmd'
        drivers/media/dvb-frontends/stv0367.c:1005:12: error: stack frame size of 7840 bytes in function 'stv0367ter_algo'
      
      None of these happen with gcc today, and almost all of these are the
      result of a single known issue in llvm.  Hopefully it will eventually
      get fixed with the clang-9 release.
      
      In the meantime, the best idea I have is to turn off asan-stack for
      clang-8 and earlier, so we can produce a kernel that is safe to run.
      
      I have posted three patches that address the frame overflow warnings
      that are not addressed by turning off asan-stack, so in combination with
      this change, we get much closer to a clean allmodconfig build, which in
      turn is necessary to do meaningful build regression testing.
      
      It is still possible to turn on the CONFIG_ASAN_STACK option on all
      versions of clang, and it's always enabled for gcc, but when
      CONFIG_COMPILE_TEST is set, the option remains invisible, so
      allmodconfig and randconfig builds (which are normally done with a
      forced CONFIG_COMPILE_TEST) will still result in a mostly clean build.
      
      Link: http://lkml.kernel.org/r/20190222222950.3997333-1-arnd@arndb.de
      Link: https://bugs.llvm.org/show_bug.cgi?id=38809
      
      
      Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
      Reviewed-by: default avatarQian Cai <cai@lca.pw>
      Reviewed-by: default avatarMark Brown <broonie@kernel.org>
      Acked-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Nick Desaulniers <ndesaulniers@google.com>
      Cc: Kostya Serebryany <kcc@google.com>
      Cc: Andrey Konovalov <andreyknvl@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6baec880
  7. Feb 28, 2019
  8. Feb 26, 2019
    • Eric Dumazet's avatar
      iov_iter: optimize page_copy_sane() · 6daef95b
      Eric Dumazet authored
      
      Avoid cache line miss dereferencing struct page if we can.
      
      page_copy_sane() mostly deals with order-0 pages.
      
      Extra cache line miss is visible on TCP recvmsg() calls dealing
      with GRO packets (typically 45 page frags are attached to one skb).
      
      Bringing the 45 struct pages into cpu cache while copying the data
      is not free, since the freeing of the skb (and associated
      page frags put_page()) can happen after cache lines have been evicted.
      
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      6daef95b
  9. Feb 25, 2019
    • Anders Roxell's avatar
      bpf: test_bpf: turn off preemption in function __run_once · fd92d664
      Anders Roxell authored
      
      When running BPF test suite the following splat occurs:
      
      [  415.930950] test_bpf: #0 TAX jited:0
      [  415.931067] BUG: assuming atomic context at lib/test_bpf.c:6674
      [  415.946169] in_atomic(): 0, irqs_disabled(): 0, pid: 11556, name: modprobe
      [  415.953176] INFO: lockdep is turned off.
      [  415.957207] CPU: 1 PID: 11556 Comm: modprobe Tainted: G        W         5.0.0-rc7-next-20190220 #1
      [  415.966328] Hardware name: HiKey Development Board (DT)
      [  415.971592] Call trace:
      [  415.974069]  dump_backtrace+0x0/0x160
      [  415.977761]  show_stack+0x24/0x30
      [  415.981104]  dump_stack+0xc8/0x114
      [  415.984534]  __cant_sleep+0xf0/0x108
      [  415.988145]  test_bpf_init+0x5e0/0x1000 [test_bpf]
      [  415.992971]  do_one_initcall+0x90/0x428
      [  415.996837]  do_init_module+0x60/0x1e4
      [  416.000614]  load_module+0x1de0/0x1f50
      [  416.004391]  __se_sys_finit_module+0xc8/0xe0
      [  416.008691]  __arm64_sys_finit_module+0x24/0x30
      [  416.013255]  el0_svc_common+0x78/0x130
      [  416.017031]  el0_svc_handler+0x38/0x78
      [  416.020806]  el0_svc+0x8/0xc
      
      Rework so that preemption is disabled when we loop over function
      'BPF_PROG_RUN(...)'.
      
      Fixes: 568f1967 ("bpf: check that BPF programs run with preemption disabled")
      Suggested-by: default avatarArnd Bergmann <arnd@arndb.de>
      Signed-off-by: default avatarAnders Roxell <anders.roxell@linaro.org>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      fd92d664
  10. Feb 22, 2019
  11. Feb 21, 2019
  12. Feb 20, 2019
  13. Feb 15, 2019
    • David Howells's avatar
      assoc_array: Fix shortcut creation · bb2ba2d7
      David Howells authored
      
      Fix the creation of shortcuts for which the length of the index key value
      is an exact multiple of the machine word size.  The problem is that the
      code that blanks off the unused bits of the shortcut value malfunctions if
      the number of bits in the last word equals machine word size.  This is due
      to the "<<" operator being given a shift of zero in this case, and so the
      mask that should be all zeros is all ones instead.  This causes the
      subsequent masking operation to clear everything rather than clearing
      nothing.
      
      Ordinarily, the presence of the hash at the beginning of the tree index key
      makes the issue very hard to test for, but in this case, it was encountered
      due to a development mistake that caused the hash output to be either 0
      (keyring) or 1 (non-keyring) only.  This made it susceptible to the
      keyctl/unlink/valid test in the keyutils package.
      
      The fix is simply to skip the blanking if the shift would be 0.  For
      example, an index key that is 64 bits long would produce a 0 shift and thus
      a 'blank' of all 1s.  This would then be inverted and AND'd onto the
      index_key, incorrectly clearing the entire last word.
      
      Fixes: 3cb98950 ("Add a generic associative array implementation.")
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarJames Morris <james.morris@microsoft.com>
      bb2ba2d7
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