# 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 <dh.herrmann@gmail.com>
# 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 <jannh@google.com>
#     Signed-off-by: Tom Gundersen <teg@jklm.no>
#     Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-ld --version
# < git log --format=%s --max-count=1 7b55851367136b1efd84d98fea81ba57a98304cf
# < make -s -j 8 ARCH=powerpc O=/kisskb/build/linus_ps3_defconfig_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-  ps3_defconfig
# make -s -j 8 ARCH=powerpc O=/kisskb/build/linus_ps3_defconfig_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-  
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:186:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c: In function 'init_srcu_struct_fields':
/kisskb/src/kernel/rcu/srcutree.c:152:32: warning: 'levelspread[<Uac80>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:100:6: note: 'levelspread[<Uac80>]' was declared here
/kisskb/src/ipc/shm.c: In function 'ksys_shmdt':
/kisskb/src/ipc/shm.c:1686:59: warning: 'file' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/bluetooth/hidp/core.c: In function 'hidp_connection_add':
/kisskb/src/net/bluetooth/hidp/core.c:1381:18: warning: 'session' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/lib/mpi/mpicoder.c: In function 'mpi_read_raw_from_sgl':
/kisskb/src/lib/mpi/mpicoder.c:352:8: warning: 'buff' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/lib/rhashtable.c: In function 'rht_deferred_worker':
/kisskb/src/lib/rhashtable.c:264:2: warning: 'next' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/lib/rhashtable.c:229:28: note: 'next' was declared here
/kisskb/src/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:339:21: note: 'pdeo' was declared here
/kisskb/src/net/ipv6/ip6_output.c: In function '__ip6_append_data.isra.35':
/kisskb/src/include/linux/skbuff.h:1338:6: warning: 'extra_uref' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/ipv6/ip6_output.c:1270:14: note: 'extra_uref' was declared here
/kisskb/src/net/core/gen_stats.c: In function '__gnet_stats_copy_basic':
/kisskb/src/net/core/gen_stats.c:161:19: warning: 'seq' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/ipv4/ip_output.c: In function '__ip_append_data.isra.41':
/kisskb/src/include/linux/skbuff.h:1338:6: warning: 'extra_uref' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/ipv4/ip_output.c:885:14: note: 'extra_uref' was declared here
/kisskb/src/net/core/dev.c: In function 'validate_xmit_skb_list':
/kisskb/src/net/core/dev.c:3405:15: warning: 'tail' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/udf/unicode.c: In function 'udf_name_conv_char':
/kisskb/src/fs/udf/unicode.c:132:8: warning: 'c' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/mac80211/tx.c: In function 'ieee80211_build_hdr':
/kisskb/src/net/mac80211/tx.c:2502:27: warning: 'chanctx_conf' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/mac80211/mlme.c: In function 'ieee80211_rx_mgmt_beacon':
/kisskb/src/net/mac80211/mlme.c:1522:3: warning: 'pwr_level_cisco' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/mac80211/mlme.c:1479:6: note: 'pwr_level_cisco' was declared here
Completed OK
# rm -rf /kisskb/build/linus_ps3_defconfig_powerpc-gcc4.6
# Build took: 0:01:47.219420