https://github.com/torvalds/linux
Revision 735f2770a770156100f534646158cb58cb8b2939 authored by Michal Hocko on 01 September 2016, 23:15:13 UTC, committed by Linus Torvalds on 02 September 2016, 00:52:02 UTC
Commit fec1d0115240 ("[PATCH] Disable CLONE_CHILD_CLEARTID for abnormal exit") has caused a subtle regression in nscd which uses CLONE_CHILD_CLEARTID to clear the nscd_certainly_running flag in the shared databases, so that the clients are notified when nscd is restarted. Now, when nscd uses a non-persistent database, clients that have it mapped keep thinking the database is being updated by nscd, when in fact nscd has created a new (anonymous) one (for non-persistent databases it uses an unlinked file as backend). The original proposal for the CLONE_CHILD_CLEARTID change claimed (https://lkml.org/lkml/2006/10/25/233): : The NPTL library uses the CLONE_CHILD_CLEARTID flag on clone() syscalls : on behalf of pthread_create() library calls. This feature is used to : request that the kernel clear the thread-id in user space (at an address : provided in the syscall) when the thread disassociates itself from the : address space, which is done in mm_release(). : : Unfortunately, when a multi-threaded process incurs a core dump (such as : from a SIGSEGV), the core-dumping thread sends SIGKILL signals to all of : the other threads, which then proceed to clear their user-space tids : before synchronizing in exit_mm() with the start of core dumping. This : misrepresents the state of process's address space at the time of the : SIGSEGV and makes it more difficult for someone to debug NPTL and glibc : problems (misleading him/her to conclude that the threads had gone away : before the fault). : : The fix below is to simply avoid the CLONE_CHILD_CLEARTID action if a : core dump has been initiated. The resulting patch from Roland (https://lkml.org/lkml/2006/10/26/269) seems to have a larger scope than the original patch asked for. It seems that limitting the scope of the check to core dumping should work for SIGSEGV issue describe above. [Changelog partly based on Andreas' description] Fixes: fec1d0115240 ("[PATCH] Disable CLONE_CHILD_CLEARTID for abnormal exit") Link: http://lkml.kernel.org/r/1471968749-26173-1-git-send-email-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Tested-by: William Preston <wpreston@suse.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Andreas Schwab <schwab@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent c4e2973
Tip revision: 735f2770a770156100f534646158cb58cb8b2939 authored by Michal Hocko on 01 September 2016, 23:15:13 UTC
kernel/fork: fix CLONE_CHILD_CLEARTID regression in nscd
kernel/fork: fix CLONE_CHILD_CLEARTID regression in nscd
Tip revision: 735f277
File | Mode | Size |
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bpf | ||
configs | ||
debug | ||
events | ||
gcov | ||
irq | ||
livepatch | ||
locking | ||
power | ||
printk | ||
rcu | ||
sched | ||
time | ||
trace | ||
.gitignore | -rw-r--r-- | 69 bytes |
Kconfig.freezer | -rw-r--r-- | 52 bytes |
Kconfig.hz | -rw-r--r-- | 1.6 KB |
Kconfig.locks | -rw-r--r-- | 4.8 KB |
Kconfig.preempt | -rw-r--r-- | 2.1 KB |
Makefile | -rw-r--r-- | 4.1 KB |
acct.c | -rw-r--r-- | 15.4 KB |
async.c | -rw-r--r-- | 9.9 KB |
audit.c | -rw-r--r-- | 53.7 KB |
audit.h | -rw-r--r-- | 11.1 KB |
audit_fsnotify.c | -rw-r--r-- | 6.1 KB |
audit_tree.c | -rw-r--r-- | 22.6 KB |
audit_watch.c | -rw-r--r-- | 14.3 KB |
auditfilter.c | -rw-r--r-- | 34.0 KB |
auditsc.c | -rw-r--r-- | 64.4 KB |
backtracetest.c | -rw-r--r-- | 2.1 KB |
bounds.c | -rw-r--r-- | 703 bytes |
capability.c | -rw-r--r-- | 12.9 KB |
cgroup.c | -rw-r--r-- | 174.5 KB |
cgroup_freezer.c | -rw-r--r-- | 12.4 KB |
cgroup_pids.c | -rw-r--r-- | 8.9 KB |
compat.c | -rw-r--r-- | 29.5 KB |
configs.c | -rw-r--r-- | 2.8 KB |
context_tracking.c | -rw-r--r-- | 6.3 KB |
cpu.c | -rw-r--r-- | 43.0 KB |
cpu_pm.c | -rw-r--r-- | 6.5 KB |
cpuset.c | -rw-r--r-- | 76.2 KB |
crash_dump.c | -rw-r--r-- | 1.3 KB |
cred.c | -rw-r--r-- | 21.5 KB |
delayacct.c | -rw-r--r-- | 4.5 KB |
dma.c | -rw-r--r-- | 3.6 KB |
elfcore.c | -rw-r--r-- | 396 bytes |
exec_domain.c | -rw-r--r-- | 1.4 KB |
exit.c | -rw-r--r-- | 43.9 KB |
extable.c | -rw-r--r-- | 4.0 KB |
fork.c | -rw-r--r-- | 51.5 KB |
freezer.c | -rw-r--r-- | 4.4 KB |
futex.c | -rw-r--r-- | 89.1 KB |
futex_compat.c | -rw-r--r-- | 4.5 KB |
groups.c | -rw-r--r-- | 5.9 KB |
hung_task.c | -rw-r--r-- | 5.9 KB |
irq_work.c | -rw-r--r-- | 4.4 KB |
jump_label.c | -rw-r--r-- | 15.2 KB |
kallsyms.c | -rw-r--r-- | 15.7 KB |
kcmp.c | -rw-r--r-- | 4.4 KB |
kcov.c | -rw-r--r-- | 6.6 KB |
kexec.c | -rw-r--r-- | 6.8 KB |
kexec_core.c | -rw-r--r-- | 39.6 KB |
kexec_file.c | -rw-r--r-- | 24.5 KB |
kexec_internal.h | -rw-r--r-- | 1.2 KB |
kmod.c | -rw-r--r-- | 19.1 KB |
kprobes.c | -rw-r--r-- | 60.7 KB |
ksysfs.c | -rw-r--r-- | 6.2 KB |
kthread.c | -rw-r--r-- | 19.2 KB |
latencytop.c | -rw-r--r-- | 7.8 KB |
membarrier.c | -rw-r--r-- | 2.4 KB |
memremap.c | -rw-r--r-- | 11.6 KB |
module-internal.h | -rw-r--r-- | 458 bytes |
module.c | -rw-r--r-- | 109.3 KB |
module_signing.c | -rw-r--r-- | 2.2 KB |
notifier.c | -rw-r--r-- | 16.3 KB |
nsproxy.c | -rw-r--r-- | 6.4 KB |
padata.c | -rw-r--r-- | 25.2 KB |
panic.c | -rw-r--r-- | 14.6 KB |
params.c | -rw-r--r-- | 24.1 KB |
pid.c | -rw-r--r-- | 15.0 KB |
pid_namespace.c | -rw-r--r-- | 10.0 KB |
profile.c | -rw-r--r-- | 14.7 KB |
ptrace.c | -rw-r--r-- | 31.6 KB |
range.c | -rw-r--r-- | 3.0 KB |
reboot.c | -rw-r--r-- | 13.3 KB |
relay.c | -rw-r--r-- | 33.4 KB |
resource.c | -rw-r--r-- | 39.3 KB |
seccomp.c | -rw-r--r-- | 23.6 KB |
signal.c | -rw-r--r-- | 94.1 KB |
smp.c | -rw-r--r-- | 19.5 KB |
smpboot.c | -rw-r--r-- | 13.2 KB |
smpboot.h | -rw-r--r-- | 601 bytes |
softirq.c | -rw-r--r-- | 18.9 KB |
stacktrace.c | -rw-r--r-- | 1.7 KB |
stop_machine.c | -rw-r--r-- | 16.7 KB |
sys.c | -rw-r--r-- | 57.6 KB |
sys_ni.c | -rw-r--r-- | 7.0 KB |
sysctl.c | -rw-r--r-- | 67.5 KB |
sysctl_binary.c | -rw-r--r-- | 50.8 KB |
task_work.c | -rw-r--r-- | 3.3 KB |
taskstats.c | -rw-r--r-- | 14.8 KB |
test_kprobes.c | -rw-r--r-- | 7.4 KB |
torture.c | -rw-r--r-- | 21.0 KB |
tracepoint.c | -rw-r--r-- | 14.5 KB |
tsacct.c | -rw-r--r-- | 5.1 KB |
uid16.c | -rw-r--r-- | 5.0 KB |
up.c | -rw-r--r-- | 1.7 KB |
user-return-notifier.c | -rw-r--r-- | 1.3 KB |
user.c | -rw-r--r-- | 5.4 KB |
user_namespace.c | -rw-r--r-- | 25.7 KB |
utsname.c | -rw-r--r-- | 3.0 KB |
utsname_sysctl.c | -rw-r--r-- | 3.0 KB |
watchdog.c | -rw-r--r-- | 29.6 KB |
workqueue.c | -rw-r--r-- | 152.2 KB |
workqueue_internal.h | -rw-r--r-- | 2.2 KB |
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