# git rev-parse -q --verify 27667f4744fc5a0f3e50910e78740bac5670d18b^{commit} 27667f4744fc5a0f3e50910e78740bac5670d18b already have revision, skipping fetch # git checkout -q -f -B kisskb 27667f4744fc5a0f3e50910e78740bac5670d18b # git clean -qxdf # git log -1 commit 27667f4744fc5a0f3e50910e78740bac5670d18b Author: Linus Torvalds Date: Wed Jul 29 22:18:16 2015 -0700 i915: temporary fix for DP MST docking station NULL pointer dereference Ted Ts'o reports that his Lenovo T540p ThinkPad crashes at boot if attached to the docking station. This is a regression that he was able to bisect to commit 8c7b5ccb7298: "drm/i915: Use atomic helpers for computing changed flags:" The reason seems to be the new call to drm_atomic_helper_check_modeset() added to intel_modeset_compute_config(), which in turn calls update_connector_routing(), and somehow ends up picking a NULL crtc for the connector state, causing the subsequent drm_crtc_index() to OOPS. Daniel Vetter says that the fundamental issue seems to be confusion in the encoder selection, and this isn't the right fix, but while he chases down the proper fix, this at least avoids the NULL pointer dereference and makes Ted's docking station work again. Reported-bisected-and-tested-by: Theodore Ts'o Cc: Daniel Vetter Cc: Mani Nikula Cc: Dave Airlie Signed-off-by: Linus Torvalds # < /opt/cross/gcc-4.6.3-nolibc/um-x86_64-linux/bin/x86_64-linux-gcc --version # < git log --format=%s --max-count=1 27667f4744fc5a0f3e50910e78740bac5670d18b # < make -j 48 ARCH=um O=/home/kisskb/slave/build/linus_um-defconfig_um-x86_64 CROSS_COMPILE=/opt/cross/gcc-4.6.3-nolibc/um-x86_64-linux/bin/x86_64-linux- SUBARCH=x86_64 defconfig kernel/time/Kconfig:157:warning: range is invalid # make -j 48 ARCH=um O=/home/kisskb/slave/build/linus_um-defconfig_um-x86_64 CROSS_COMPILE=/opt/cross/gcc-4.6.3-nolibc/um-x86_64-linux/bin/x86_64-linux- SUBARCH=x86_64 make[1]: Entering directory '/home/kisskb/slave/build/linus_um-defconfig_um-x86_64' GEN ./Makefile scripts/kconfig/conf --silentoldconfig arch/x86/um/Kconfig kernel/time/Kconfig:157:warning: range is invalid CHK include/generated/uapi/linux/version.h UPD include/generated/uapi/linux/version.h HOSTCC scripts/basic/bin2c WRAP arch/um/include/generated/asm/barrier.h WRAP arch/um/include/generated/asm/bug.h WRAP arch/um/include/generated/asm/clkdev.h WRAP arch/um/include/generated/asm/cputime.h WRAP arch/um/include/generated/asm/current.h WRAP arch/um/include/generated/asm/delay.h WRAP arch/um/include/generated/asm/device.h WRAP arch/um/include/generated/asm/emergency-restart.h WRAP arch/um/include/generated/asm/exec.h WRAP arch/um/include/generated/asm/ftrace.h WRAP arch/um/include/generated/asm/futex.h WRAP arch/um/include/generated/asm/hardirq.h WRAP arch/um/include/generated/asm/hw_irq.h WRAP arch/um/include/generated/asm/io.h WRAP arch/um/include/generated/asm/irq_regs.h WRAP arch/um/include/generated/asm/irq_work.h WRAP arch/um/include/generated/asm/kdebug.h WRAP arch/um/include/generated/asm/mcs_spinlock.h WRAP arch/um/include/generated/asm/mm-arch-hooks.h WRAP arch/um/include/generated/asm/mutex.h WRAP arch/um/include/generated/asm/param.h WRAP arch/um/include/generated/asm/pci.h WRAP arch/um/include/generated/asm/percpu.h WRAP arch/um/include/generated/asm/preempt.h WRAP arch/um/include/generated/asm/switch_to.h WRAP arch/um/include/generated/asm/topology.h WRAP arch/um/include/generated/asm/trace_clock.h WRAP arch/um/include/generated/asm/xor.h CHK include/config/kernel.release GEN ./Makefile HOSTCC scripts/kallsyms CC scripts/mod/empty.o HOSTCC scripts/mod/mk_elfconfig CC scripts/mod/devicetable-offsets.s GEN scripts/mod/devicetable-offsets.h MKELF scripts/mod/elfconfig.h HOSTCC scripts/mod/modpost.o HOSTCC scripts/mod/file2alias.o HOSTCC scripts/mod/sumversion.o UPD include/config/kernel.release SYSTBL arch/x86/entry/syscalls/../../include/generated/asm/syscalls_32.h SYSHDR arch/x86/entry/syscalls/../../include/generated/asm/unistd_32_ia32.h SYSHDR arch/x86/entry/syscalls/../../include/generated/asm/unistd_64_x32.h SYSTBL arch/x86/entry/syscalls/../../include/generated/asm/syscalls_64.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 SYSHDR arch/x86/entry/syscalls/../../include/generated/uapi/asm/unistd_x32.h Using /home/kisskb/slave/src as source for kernel CHK include/generated/utsrelease.h UPD include/generated/utsrelease.h HOSTLD scripts/mod/modpost HOSTCC scripts/unifdef CC arch/x86/um/user-offsets.s In file included from /usr/include/features.h:374:0, from /usr/include/stdio.h:27, from /home/kisskb/slave/src/arch/x86/um/user-offsets.c:1: /opt/cross/gcc-4.6.3-nolibc/x86_64-linux/lib/gcc/x86_64-linux/4.6.3/../../../../x86_64-linux/include/sys/cdefs.h:385:27: fatal error: bits/wordsize.h: No such file or directory compilation terminated. /home/kisskb/slave/src/scripts/Makefile.build:153: recipe for target 'arch/x86/um/user-offsets.s' failed make[2]: *** [arch/x86/um/user-offsets.s] Error 1 arch/um/Makefile:150: recipe for target 'arch/x86/um/user-offsets.s' failed make[1]: *** [arch/x86/um/user-offsets.s] Error 2 make[1]: Leaving directory '/home/kisskb/slave/build/linus_um-defconfig_um-x86_64' Makefile:146: recipe for target 'sub-make' failed make: *** [sub-make] Error 2 Command 'make -j 48 ARCH=um O=/home/kisskb/slave/build/linus_um-defconfig_um-x86_64 CROSS_COMPILE=/opt/cross/gcc-4.6.3-nolibc/um-x86_64-linux/bin/x86_64-linux- SUBARCH=x86_64 ' returned non-zero exit status 2 # rm -rf /home/kisskb/slave/build/linus_um-defconfig_um-x86_64 # Build took: 0:00:04.451849