# git rev-parse -q --verify 44960f2a7b63e224b1091b3e1d6f60e0cdf4be0c^{commit}
44960f2a7b63e224b1091b3e1d6f60e0cdf4be0c
already have revision, skipping fetch
# git checkout -q -f -B kisskb 44960f2a7b63e224b1091b3e1d6f60e0cdf4be0c
# git clean -qxdf
# < git log -1
# commit 44960f2a7b63e224b1091b3e1d6f60e0cdf4be0c
# Author: John Stultz <john.stultz@linaro.org>
# Date:   Tue Jul 31 10:17:04 2018 -0700
# 
#     staging: ashmem: Fix SIGBUS crash when traversing mmaped ashmem pages
#     
#     Amit Pundir and Youling in parallel reported crashes with recent
#     mainline kernels running Android:
#     
#       F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
#       F DEBUG   : Build fingerprint: 'Android/db410c32_only/db410c32_only:Q/OC-MR1/102:userdebug/test-key
#       F DEBUG   : Revision: '0'
#       F DEBUG   : ABI: 'arm'
#       F DEBUG   : pid: 2261, tid: 2261, name: zygote  >>> zygote <<<
#       F DEBUG   : signal 7 (SIGBUS), code 2 (BUS_ADRERR), fault addr 0xec00008
#       ... <snip> ...
#       F DEBUG   : backtrace:
#       F DEBUG   :     #00 pc 00001c04  /system/lib/libc.so (memset+48)
#       F DEBUG   :     #01 pc 0010c513  /system/lib/libart.so (create_mspace_with_base+82)
#       F DEBUG   :     #02 pc 0015c601  /system/lib/libart.so (art::gc::space::DlMallocSpace::CreateMspace(void*, unsigned int, unsigned int)+40)
#       F DEBUG   :     #03 pc 0015c3ed  /system/lib/libart.so (art::gc::space::DlMallocSpace::CreateFromMemMap(art::MemMap*, std::__1::basic_string<char, std::__ 1::char_traits<char>, std::__1::allocator<char>> const&, unsigned int, unsigned int, unsigned int, unsigned int, bool)+36)
#       ...
#     
#     This was bisected back to commit bfd40eaff5ab ("mm: fix
#     vma_is_anonymous() false-positives").
#     
#     create_mspace_with_base() in the trace above, utilizes ashmem, and with
#     ashmem, for shared mappings we use shmem_zero_setup(), which sets the
#     vma->vm_ops to &shmem_vm_ops.  But for private ashmem mappings nothing
#     sets the vma->vm_ops.
#     
#     Looking at the problematic patch, it seems to add a requirement that one
#     call vma_set_anonymous() on a vma, otherwise the dummy_vm_ops will be
#     used.  Using the dummy_vm_ops seem to triggger SIGBUS when traversing
#     unmapped pages.
#     
#     Thus, this patch adds a call to vma_set_anonymous() for ashmem private
#     mappings and seems to avoid the reported problem.
#     
#     Fixes: bfd40eaff5ab ("mm: fix vma_is_anonymous() false-positives")
#     Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
#     Cc: Andrew Morton <akpm@linux-foundation.org>
#     Cc: Dmitry Vyukov <dvyukov@google.com>
#     Cc: Oleg Nesterov <oleg@redhat.com>
#     Cc: Andrea Arcangeli <aarcange@redhat.com>
#     Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
#     Cc: Hugh Dickins <hughd@google.com>
#     Cc: Joel Fernandes <joelaf@google.com>
#     Cc: Colin Cross <ccross@google.com>
#     Cc: Matthew Wilcox <willy@infradead.org>
#     Reported-by: Amit Pundir <amit.pundir@linaro.org>
#     Reported-by: Youling 257 <youling257@gmail.com>
#     Signed-off-by: John Stultz <john.stultz@linaro.org>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-5.2.0-nolibc/powerpc64le-linux/bin/powerpc64le-linux-gcc --version
# < git log --format=%s --max-count=1 44960f2a7b63e224b1091b3e1d6f60e0cdf4be0c
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/linus_ppc64le_defconfig+NO_KVM_ppc64le CROSS_COMPILE=/opt/cross/kisskb/gcc-5.2.0-nolibc/powerpc64le-linux/bin/powerpc64le-linux-  ppc64le_defconfig
# Added to kconfig CONFIG_KVM_BOOK3S_64=n
# Added to kconfig CONFIG_KVM=n
# yes \n | make -s -j 48 ARCH=powerpc O=/kisskb/build/linus_ppc64le_defconfig+NO_KVM_ppc64le CROSS_COMPILE=/opt/cross/kisskb/gcc-5.2.0-nolibc/powerpc64le-linux/bin/powerpc64le-linux-  oldconfig
yes: standard output: Broken pipe
yes: write error
# make -s -j 48 ARCH=powerpc O=/kisskb/build/linus_ppc64le_defconfig+NO_KVM_ppc64le CROSS_COMPILE=/opt/cross/kisskb/gcc-5.2.0-nolibc/powerpc64le-linux/bin/powerpc64le-linux-  
WARNING: modpost: Found 3 section mismatch(es).
To see full details build your kernel with:
'make CONFIG_DEBUG_SECTION_MISMATCH=y'
Completed OK
# rm -rf /kisskb/build/linus_ppc64le_defconfig+NO_KVM_ppc64le
# Build took: 0:03:05.290790