# 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/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc-gcc --version # < /opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc-ld --version # < git log --format=%s --max-count=1 7b55851367136b1efd84d98fea81ba57a98304cf # < make -s -j 8 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- axs101_defconfig # Added to kconfig CONFIG_INITRAMFS_SOURCE="" # yes \n | make -s -j 8 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- oldconfig yes: standard output: Broken pipe # make -s -j 8 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- /kisskb/src/arch/arc/boot/dts/axs10x_mb.dtsi:221.15-225.6: Warning (i2c_bus_reg): /axs10x_mb/i2c@0x1f000/eeprom@0x54: I2C bus unit address format error, expected "54" /kisskb/src/arch/arc/boot/dts/axs10x_mb.dtsi:227.15-231.6: Warning (i2c_bus_reg): /axs10x_mb/i2c@0x1f000/eeprom@0x57: I2C bus unit address format error, expected "57" /kisskb/src/arch/arc/mm/tlb.c: In function 'do_tlb_overlap_fault': /kisskb/src/arch/arc/mm/tlb.c:914:2: warning: variable length array 'pd0' is used [-Wvla] unsigned int pd0[mmu->ways]; ^ In file included from /kisskb/src/mm/memblock.c:13:0: /kisskb/src/mm/memblock.c: In function '__free_pages_memory': /kisskb/src/include/linux/kernel.h:846:29: warning: comparison of distinct pointer types lacks a cast [enabled by default] (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) ^ /kisskb/src/include/linux/kernel.h:860:4: note: in expansion of macro '__typecheck' (__typecheck(x, y) && __no_side_effects(x, y)) ^ /kisskb/src/include/linux/kernel.h:870:24: note: in expansion of macro '__safe_cmp' __builtin_choose_expr(__safe_cmp(x, y), \ ^ /kisskb/src/include/linux/kernel.h:879:19: note: in expansion of macro '__careful_cmp' #define min(x, y) __careful_cmp(x, y, <) ^ /kisskb/src/mm/memblock.c:1889:11: note: in expansion of macro 'min' order = min(MAX_ORDER - 1UL, __ffs(start)); ^ In file included from /kisskb/src/arch/arc/include/asm/atomic.h:16:0, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/arc/include/asm/bitops.h:429, from /kisskb/src/include/linux/bitops.h:19, from /kisskb/src/include/linux/kernel.h:11, from /kisskb/src/include/linux/list.h:9, from /kisskb/src/include/linux/wait.h:7, from /kisskb/src/include/linux/wait_bit.h:8, from /kisskb/src/include/linux/fs.h:6, from /kisskb/src/fs/nfs/nfs3acl.c:2: /kisskb/src/fs/nfs/nfs3acl.c: In function 'nfs3_abort_get_acl': /kisskb/src/arch/arc/include/asm/cmpxchg.h:95:29: warning: value computed is not used [-Wunused-value] #define cmpxchg(ptr, o, n) ((typeof(*(ptr)))__cmpxchg((ptr), \ ^ /kisskb/src/fs/nfs/nfs3acl.c:44:2: note: in expansion of macro 'cmpxchg' cmpxchg(p, sentinel, ACL_NOT_CACHED); ^ In file included from /kisskb/src/arch/arc/include/asm/atomic.h:16:0, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/arc/include/asm/bitops.h:429, from /kisskb/src/include/linux/bitops.h:19, from /kisskb/src/include/linux/kernel.h:11, from /kisskb/src/include/linux/list.h:9, from /kisskb/src/include/linux/module.h:9, from /kisskb/src/net/core/filter.c:24: /kisskb/src/net/core/filter.c: In function 'bpf_clear_redirect_map': /kisskb/src/arch/arc/include/asm/cmpxchg.h:95:29: warning: value computed is not used [-Wunused-value] #define cmpxchg(ptr, o, n) ((typeof(*(ptr)))__cmpxchg((ptr), \ ^ /kisskb/src/net/core/filter.c:3469:4: note: in expansion of macro 'cmpxchg' cmpxchg(&ri->map, map, NULL); ^ /kisskb/src/net/ipv4/tcp_input.c: In function 'tcp_data_queue': /kisskb/src/net/ipv4/tcp_input.c:4324:49: warning: array subscript is above array bounds [-Warray-bounds] tp->selective_acks[i-1] = tp->selective_acks[i]; ^ In file included from /kisskb/src/arch/arc/include/asm/atomic.h:16:0, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/arc/include/asm/bitops.h:429, from /kisskb/src/include/linux/bitops.h:19, from /kisskb/src/include/linux/kernel.h:11, from /kisskb/src/fs/posix_acl.c:13: /kisskb/src/fs/posix_acl.c: In function 'get_acl': /kisskb/src/arch/arc/include/asm/cmpxchg.h:95:29: warning: value computed is not used [-Wunused-value] #define cmpxchg(ptr, o, n) ((typeof(*(ptr)))__cmpxchg((ptr), \ ^ /kisskb/src/fs/posix_acl.c:147:3: note: in expansion of macro 'cmpxchg' cmpxchg(p, sentinel, ACL_NOT_CACHED); ^ Completed OK # rm -rf /kisskb/build/linus_axs101_defconfig_arcompact # Build took: 0:01:19.640784