# git rev-parse -q --verify 7b55851367136b1efd84d98fea81ba57a98304cf^{commit} 7b55851367136b1efd84d98fea81ba57a98304cf already have revision, skipping fetch # git checkout -q -f -B kisskb 7b55851367136b1efd84d98fea81ba57a98304cf # git clean -qxdf # < git log -1 # commit 7b55851367136b1efd84d98fea81ba57a98304cf # Author: David Herrmann # Date: Tue Jan 8 13:58:52 2019 +0100 # # fork: record start_time late # # This changes the fork(2) syscall to record the process start_time after # initializing the basic task structure but still before making the new # process visible to user-space. # # Technically, we could record the start_time anytime during fork(2). But # this might lead to scenarios where a start_time is recorded long before # a process becomes visible to user-space. For instance, with # userfaultfd(2) and TLS, user-space can delay the execution of fork(2) # for an indefinite amount of time (and will, if this causes network # access, or similar). # # By recording the start_time late, it much closer reflects the point in # time where the process becomes live and can be observed by other # processes. # # Lastly, this makes it much harder for user-space to predict and control # the start_time they get assigned. Previously, user-space could fork a # process and stall it in copy_thread_tls() before its pid is allocated, # but after its start_time is recorded. This can be misused to later-on # cycle through PIDs and resume the stalled fork(2) yielding a process # that has the same pid and start_time as a process that existed before. # This can be used to circumvent security systems that identify processes # by their pid+start_time combination. # # Even though user-space was always aware that start_time recording is # flaky (but several projects are known to still rely on start_time-based # identification), changing the start_time to be recorded late will help # mitigate existing attacks and make it much harder for user-space to # control the start_time a process gets assigned. # # Reported-by: Jann Horn # Signed-off-by: Tom Gundersen # Signed-off-by: David Herrmann # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version # < git log --format=%s --max-count=1 7b55851367136b1efd84d98fea81ba57a98304cf # < make -s -j 8 ARCH=powerpc O=/kisskb/build/linus-rand_randconfig+ppc64le_ppc64le-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- randconfig KCONFIG_SEED=0xD9EB19EE # Added to kconfig CONFIG_STANDALONE=y # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_MODULE_SIG=n # Added to kconfig CONFIG_CPU_BIG_ENDIAN=n # Added to kconfig CONFIG_CPU_LITTLE_ENDIAN=y # Added to kconfig CONFIG_PPC64=y # Added to kconfig CONFIG_PPC_BOOK3E_64=n # Added to kconfig CONFIG_PPC_BOOK3S_64=y # Added to kconfig CONFIG_PPC_DISABLE_WERROR=y # Added to kconfig CONFIG_SECTION_MISMATCH_WARN_ONLY=y # Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y # Added to kconfig CONFIG_LD_HEAD_STUB_CATCH=y # yes \n | make -s -j 8 ARCH=powerpc O=/kisskb/build/linus-rand_randconfig+ppc64le_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 8 ARCH=powerpc O=/kisskb/build/linus-rand_randconfig+ppc64le_ppc64le-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- /kisskb/src/block/blk-cgroup.c: In function 'blkg_prfill_rwstat': /kisskb/src/block/blk-cgroup.c:607:1: warning: the frame size of 1120 bytes is larger than 1024 bytes [-Wframe-larger-than=] } ^ /kisskb/src/block/blk-cgroup.c: In function 'blkg_prfill_rwstat_field': /kisskb/src/block/blk-cgroup.c:616:1: warning: the frame size of 1120 bytes is larger than 1024 bytes [-Wframe-larger-than=] } ^ /kisskb/src/block/blk-cgroup.c: In function 'blkcg_print_stat': /kisskb/src/block/blk-cgroup.c:1015:1: warning: the frame size of 1120 bytes is larger than 1024 bytes [-Wframe-larger-than=] } ^ /kisskb/src/block/bfq-cgroup.c: In function 'bfqg_prfill_sectors': /kisskb/src/block/bfq-cgroup.c:974:1: warning: the frame size of 1120 bytes is larger than 1024 bytes [-Wframe-larger-than=] } ^ /kisskb/src/block/bfq-cgroup.c: In function 'bfqg_stats_set_start_empty_time': /kisskb/src/block/bfq-cgroup.c:121:1: warning: the frame size of 1120 bytes is larger than 1024 bytes [-Wframe-larger-than=] } ^ /kisskb/src/block/bfq-cgroup.c: In function 'bfqg_stats_update_avg_queue_size': /kisskb/src/block/bfq-cgroup.c:153:1: warning: the frame size of 1120 bytes is larger than 1024 bytes [-Wframe-larger-than=] } ^ /kisskb/src/drivers/gpu/drm/amd/amdgpu/soc15.c: In function 'soc15_set_ip_blocks': /kisskb/src/drivers/gpu/drm/amd/amdgpu/soc15.c:552:3: warning: #warning "Enable CONFIG_DRM_AMD_DC for display support on SOC15." [-Wcpp] # warning "Enable CONFIG_DRM_AMD_DC for display support on SOC15." ^ /kisskb/src/drivers/gpu/drm/amd/amdgpu/soc15.c:573:3: warning: #warning "Enable CONFIG_DRM_AMD_DC for display support on SOC15." [-Wcpp] # warning "Enable CONFIG_DRM_AMD_DC for display support on SOC15." ^ 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-rand_randconfig+ppc64le_ppc64le-gcc5 # Build took: 0:04:48.556494