# 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/br-xtensa-full-2016.08-613-ge98b4dd/bin/xtensa-linux-gcc --version
# < /opt/cross/kisskb/br-xtensa-full-2016.08-613-ge98b4dd/bin/xtensa-linux-ld --version
# < git log --format=%s --max-count=1 7b55851367136b1efd84d98fea81ba57a98304cf
# < make -s -j 8 ARCH=xtensa O=/kisskb/build/linus_xtensa-allmodconfig_xtensa CROSS_COMPILE=/opt/cross/kisskb/br-xtensa-full-2016.08-613-ge98b4dd/bin/xtensa-linux-  allmodconfig
drivers/staging/mt7621-dts/Kconfig:4:warning: 'BUILTIN_DTB' has wrong type. 'select' only accept arguments of bool and tristate type
# Added to kconfig CONFIG_BUILD_DOCSRC=n
# Added to kconfig CONFIG_MODULE_SIG=n
# Added to kconfig CONFIG_SAMPLES=n
# yes \n | make -s -j 8 ARCH=xtensa O=/kisskb/build/linus_xtensa-allmodconfig_xtensa CROSS_COMPILE=/opt/cross/kisskb/br-xtensa-full-2016.08-613-ge98b4dd/bin/xtensa-linux-  oldconfig
yes: standard output: Broken pipe
# make -s -j 8 ARCH=xtensa O=/kisskb/build/linus_xtensa-allmodconfig_xtensa CROSS_COMPILE=/opt/cross/kisskb/br-xtensa-full-2016.08-613-ge98b4dd/bin/xtensa-linux-  
drivers/staging/mt7621-dts/Kconfig:4:warning: 'BUILTIN_DTB' has wrong type. 'select' only accept arguments of bool and tristate type
<stdin>:1333:2: warning: #warning syscall io_pgetevents not implemented [-Wcpp]
<stdin>:1336:2: warning: #warning syscall rseq not implemented [-Wcpp]
/kisskb/src/arch/xtensa/kernel/pci.c:45:32: warning: 'pci_ctrl_tail' defined but not used [-Wunused-variable]
 static struct pci_controller **pci_ctrl_tail = &pci_ctrl_head;
                                ^
/kisskb/src/fs/cifs/cifssmb.c: In function '__cifs_reconnect_tcon':
/kisskb/src/fs/cifs/cifssmb.c:186:1: warning: the frame size of 1344 bytes is larger than 1024 bytes [-Wframe-larger-than=]
 }
 ^
/kisskb/src/fs/cifs/smb2pdu.c: In function '__smb2_reconnect':
/kisskb/src/fs/cifs/smb2pdu.c:220:1: warning: the frame size of 1344 bytes is larger than 1024 bytes [-Wframe-larger-than=]
 }
 ^
./usr/include/asm/setup.h:17: userspace cannot reference function or variable defined in the kernel
/kisskb/src/drivers/char/tpm/tpm2-cmd.c: In function 'tpm2_unseal_trusted':
/kisskb/src/drivers/char/tpm/tpm2-cmd.c:668:2: warning: 'blob_handle' may be used uninitialized in this function [-Wmaybe-uninitialized]
  tpm2_flush_context_cmd(chip, blob_handle, TPM_TRANSMIT_UNLOCKED);
  ^
In file included from /kisskb/src/arch/xtensa/include/asm/atomic.h:21:0,
                 from /kisskb/src/include/linux/atomic.h:7,
                 from /kisskb/src/include/asm-generic/bitops/atomic.h:5,
                 from /kisskb/src/arch/xtensa/include/asm/bitops.h:222,
                 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/ocfs2/file.c:27:
/kisskb/src/fs/ocfs2/file.c: In function 'ocfs2_file_write_iter':
/kisskb/src/arch/xtensa/include/asm/cmpxchg.h:139:3: warning: value computed is not used [-Wunused-value]
  ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
   ^
/kisskb/src/fs/ocfs2/file.c:2386:3: note: in expansion of macro 'xchg'
   xchg(&iocb->ki_complete, saved_ki_complete);
   ^
/kisskb/src/drivers/i2c/i2c-core-base.c: In function 'i2c_generic_scl_recovery':
/kisskb/src/drivers/i2c/i2c-core-base.c:235:5: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if (ret == -EOPNOTSUPP)
     ^
/kisskb/src/drivers/input/joystick/analog.c:172:2: warning: #warning Precise timer not defined for this architecture. [-Wcpp]
 #warning Precise timer not defined for this architecture.
  ^
In file included from /kisskb/src/include/linux/rwsem.h:16:0,
                 from /kisskb/src/include/linux/notifier.h:15,
                 from /kisskb/src/include/linux/clk.h:17,
                 from /kisskb/src/drivers/tty/serial/sh-sci.c:24:
/kisskb/src/drivers/tty/serial/sh-sci.c: In function 'sci_submit_rx':
/kisskb/src/include/linux/spinlock.h:279:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
   _raw_spin_unlock_irqrestore(lock, flags); \
   ^
/kisskb/src/drivers/tty/serial/sh-sci.c:1338:16: note: 'flags' was declared here
  unsigned long flags;
                ^
In file included from /kisskb/src/arch/xtensa/include/asm/atomic.h:21:0,
                 from /kisskb/src/include/linux/atomic.h:7,
                 from /kisskb/src/include/asm-generic/bitops/atomic.h:5,
                 from /kisskb/src/arch/xtensa/include/asm/bitops.h:222,
                 from /kisskb/src/include/linux/bitops.h:19,
                 from /kisskb/src/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c:11:
/kisskb/src/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c: In function 'ixgbevf_xdp_setup':
/kisskb/src/arch/xtensa/include/asm/cmpxchg.h:139:3: warning: value computed is not used [-Wunused-value]
  ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
   ^
/kisskb/src/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c:4471:4: note: in expansion of macro 'xchg'
    xchg(&adapter->rx_ring[i]->xdp_prog, adapter->xdp_prog);
    ^
/kisskb/src/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c: In function 'mlx5e_grp_sw_update_stats':
/kisskb/src/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c:217:1: warning: the frame size of 1200 bytes is larger than 1024 bytes [-Wframe-larger-than=]
 }
 ^
Completed OK
# rm -rf /kisskb/build/linus_xtensa-allmodconfig_xtensa
# Build took: 0:17:46.527497