# git rev-parse -q --verify 38e088546522e1e86d2b8f401a1354ad3a9b3303^{commit}
38e088546522e1e86d2b8f401a1354ad3a9b3303
already have revision, skipping fetch
# git checkout -q -f -B kisskb 38e088546522e1e86d2b8f401a1354ad3a9b3303
# git clean -qxdf
# git log -1
commit 38e088546522e1e86d2b8f401a1354ad3a9b3303
Author: Lorenzo Stoakes <lstoakes@gmail.com>
Date:   Sun Sep 11 23:54:25 2016 +0100

    mm: check VMA flags to avoid invalid PROT_NONE NUMA balancing
    
    The NUMA balancing logic uses an arch-specific PROT_NONE page table flag
    defined by pte_protnone() or pmd_protnone() to mark PTEs or huge page
    PMDs respectively as requiring balancing upon a subsequent page fault.
    User-defined PROT_NONE memory regions which also have this flag set will
    not normally invoke the NUMA balancing code as do_page_fault() will send
    a segfault to the process before handle_mm_fault() is even called.
    
    However if access_remote_vm() is invoked to access a PROT_NONE region of
    memory, handle_mm_fault() is called via faultin_page() and
    __get_user_pages() without any access checks being performed, meaning
    the NUMA balancing logic is incorrectly invoked on a non-NUMA memory
    region.
    
    A simple means of triggering this problem is to access PROT_NONE mmap'd
    memory using /proc/self/mem which reliably results in the NUMA handling
    functions being invoked when CONFIG_NUMA_BALANCING is set.
    
    This issue was reported in bugzilla (issue 99101) which includes some
    simple repro code.
    
    There are BUG_ON() checks in do_numa_page() and do_huge_pmd_numa_page()
    added at commit c0e7cad to avoid accidentally provoking strange
    behaviour by attempting to apply NUMA balancing to pages that are in
    fact PROT_NONE.  The BUG_ON()'s are consistently triggered by the repro.
    
    This patch moves the PROT_NONE check into mm/memory.c rather than
    invoking BUG_ON() as faulting in these pages via faultin_page() is a
    valid reason for reaching the NUMA check with the PROT_NONE page table
    flag set and is therefore not always a bug.
    
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=99101
    Reported-by: Trevor Saunders <tbsaunde@tbsaunde.org>
    Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
    Acked-by: Rik van Riel <riel@redhat.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-gcc --version
# < git log --format=%s --max-count=1 38e088546522e1e86d2b8f401a1354ad3a9b3303
# < make -j 10 ARCH=i386 O=/home/kisskb/slave/build/linus_i386-randconfig_i386 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-  randconfig
KCONFIG_SEED=0xFEA90F1E
# Added to kconfig CONFIG_STANDALONE=y
# Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y
# yes \n | make -j 10 ARCH=i386 O=/home/kisskb/slave/build/linus_i386-randconfig_i386 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-  oldconfig
yes: standard output: Broken pipe
yes: write error
# make -j 10 ARCH=i386 O=/home/kisskb/slave/build/linus_i386-randconfig_i386 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-  
make[1]: Entering directory '/home/kisskb/slave/build/linus_i386-randconfig_i386'
  GEN     ./Makefile
scripts/kconfig/conf  --silentoldconfig Kconfig
  SYSTBL  arch/x86/entry/syscalls/../../include/generated/asm/syscalls_32.h
  SYSHDR  arch/x86/entry/syscalls/../../include/generated/uapi/asm/unistd_32.h
  SYSHDR  arch/x86/entry/syscalls/../../include/generated/uapi/asm/unistd_64.h
  CHK     include/config/kernel.release
  SYSHDR  arch/x86/entry/syscalls/../../include/generated/uapi/asm/unistd_x32.h
  HOSTCC  scripts/basic/bin2c
Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
/home/kisskb/slave/src/Makefile:1048: recipe for target 'prepare-compiler-check' failed
make[1]: *** [prepare-compiler-check] Error 1
make[1]: *** Waiting for unfinished jobs....
  UPD     include/config/kernel.release
make[1]: *** wait: No child processes.  Stop.
Makefile:150: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2
Command 'make -j 10 ARCH=i386 O=/home/kisskb/slave/build/linus_i386-randconfig_i386 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-  ' returned non-zero exit status 2
# rm -rf /home/kisskb/slave/build/linus_i386-randconfig_i386
# Build took: 0:00:08.300685