# git rev-parse -q --verify 61a8426c92ba30d403a1f072e29d713184539cc1^{commit}
61a8426c92ba30d403a1f072e29d713184539cc1
already have revision, skipping fetch
# git checkout -q -f -B kisskb 61a8426c92ba30d403a1f072e29d713184539cc1
# git clean -qxdf
# < git log -1
# commit 61a8426c92ba30d403a1f072e29d713184539cc1
# Author: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
# Date:   Mon Nov 26 20:05:04 2018 +0530
# 
#     powerpc/mm/hash: Handle user access of kernel address gracefully
#     
#     In commit 2865d08dd9ea ("powerpc/mm: Move the DSISR_PROTFAULT sanity
#     check") we moved the protection fault access check before the vma
#     lookup. That means we hit that WARN_ON when user space accesses a
#     kernel address. Before that commit this was handled by find_vma() not
#     finding vma for the kernel address and considering that access as bad
#     area access.
#     
#     Avoid the confusing WARN_ON and convert that to a ratelimited printk.
#     
#     With the patch we now get:
#     
#     for load:
#       a.out[5997]: User access of kernel address (c00000000000dea0) - exploit attempt? (uid: 1000)
#       a.out[5997]: segfault (11) at c00000000000dea0 nip 1317c0798 lr 7fff80d6441c code 1 in a.out[1317c0000+10000]
#       a.out[5997]: code: 60000000 60420000 3c4c0002 38427790 4bffff20 3c4c0002 38427784 fbe1fff8
#       a.out[5997]: code: f821ffc1 7c3f0b78 60000000 e9228030 <89290000> 993f002f 60000000 383f0040
#     
#     for exec:
#       a.out[6067]: User access of kernel address (c00000000000dea0) - exploit attempt? (uid: 1000)
#       a.out[6067]: segfault (11) at c00000000000dea0 nip c00000000000dea0 lr 129d507b0 code 1
#       a.out[6067]: Bad NIP, not dumping instructions.
#     
#     Fixes: 2865d08dd9ea ("powerpc/mm: Move the DSISR_PROTFAULT sanity check")
#     Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
#     Tested-by: Breno Leitao <leitao@debian.org>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < git log --format=%s --max-count=1 61a8426c92ba30d403a1f072e29d713184539cc1
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_powernv_defconfig+NO_NUMA_ppc64le-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  powernv_defconfig
# Added to kconfig CONFIG_NUMA=n
# yes \n | make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_powernv_defconfig+NO_NUMA_ppc64le-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  oldconfig
yes: standard output: Broken pipe
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_powernv_defconfig+NO_NUMA_ppc64le-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
WARNING: modpost: Found 2 section mismatch(es).
To see full details build your kernel with:
'make CONFIG_DEBUG_SECTION_MISMATCH=y'
Completed OK
# rm -rf /kisskb/build/powerpc-next_powernv_defconfig+NO_NUMA_ppc64le-gcc5
# Build took: 0:02:35.218775