linux/kernel
Christian Brauner c3b7112df8
fork: do not release lock that wasn't taken
Avoid calling cgroup_threadgroup_change_end() without having called
cgroup_threadgroup_change_begin() first.

During process creation we need to check whether the cgroup we are in
allows us to fork. To perform this check the cgroup needs to guard itself
against threadgroup changes and takes a lock.
Prior to CLONE_PIDFD the cleanup target "bad_fork_free_pid" would also need
to call cgroup_threadgroup_change_end() because said lock had already been
taken.
However, this is not the case anymore with the addition of CLONE_PIDFD. We
are now allocating a pidfd before we check whether the cgroup we're in can
fork and thus prior to taking the lock. So when copy_process() fails at the
right step it would release a lock we haven't taken.
This bug is not even very subtle to be honest. It's just not very clear
from the naming of cgroup_threadgroup_change_{begin,end}() that a lock is
taken.

Here's the relevant splat:

entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fec849
Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90
90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000ffed5a8c EFLAGS: 00000246 ORIG_RAX: 0000000000000078
RAX: ffffffffffffffda RBX: 0000000000003ffc RCX: 0000000000000000
RDX: 00000000200005c0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000012 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(depth <= 0)
WARNING: CPU: 1 PID: 7744 at kernel/locking/lockdep.c:4052 __lock_release
kernel/locking/lockdep.c:4052 [inline]
WARNING: CPU: 1 PID: 7744 at kernel/locking/lockdep.c:4052
lock_release+0x667/0xa00 kernel/locking/lockdep.c:4321
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 7744 Comm: syz-executor007 Not tainted 5.1.0+ #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  panic+0x2cb/0x65c kernel/panic.c:214
  __warn.cold+0x20/0x45 kernel/panic.c:566
  report_bug+0x263/0x2b0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:179 [inline]
  fixup_bug arch/x86/kernel/traps.c:174 [inline]
  do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
  do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:972
RIP: 0010:__lock_release kernel/locking/lockdep.c:4052 [inline]
RIP: 0010:lock_release+0x667/0xa00 kernel/locking/lockdep.c:4321
Code: 0f 85 a0 03 00 00 8b 35 77 66 08 08 85 f6 75 23 48 c7 c6 a0 55 6b 87
48 c7 c7 40 25 6b 87 4c 89 85 70 ff ff ff e8 b7 a9 eb ff <0f> 0b 4c 8b 85
70 ff ff ff 4c 89 ea 4c 89 e6 4c 89 c7 e8 52 63 ff
RSP: 0018:ffff888094117b48 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 1ffff11012822f6f RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815af236 RDI: ffffed1012822f5b
RBP: ffff888094117c00 R08: ffff888092bfc400 R09: fffffbfff113301d
R10: fffffbfff113301c R11: ffffffff889980e3 R12: ffffffff8a451df8
R13: ffffffff8142e71f R14: ffffffff8a44cc80 R15: ffff888094117bd8
  percpu_up_read.constprop.0+0xcb/0x110 include/linux/percpu-rwsem.h:92
  cgroup_threadgroup_change_end include/linux/cgroup-defs.h:712 [inline]
  copy_process.part.0+0x47ff/0x6710 kernel/fork.c:2222
  copy_process kernel/fork.c:1772 [inline]
  _do_fork+0x25d/0xfd0 kernel/fork.c:2338
  __do_compat_sys_x86_clone arch/x86/ia32/sys_ia32.c:240 [inline]
  __se_compat_sys_x86_clone arch/x86/ia32/sys_ia32.c:236 [inline]
  __ia32_compat_sys_x86_clone+0xbc/0x140 arch/x86/ia32/sys_ia32.c:236
  do_syscall_32_irqs_on arch/x86/entry/common.c:334 [inline]
  do_fast_syscall_32+0x281/0xd54 arch/x86/entry/common.c:405
  entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fec849
Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90
90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000ffed5a8c EFLAGS: 00000246 ORIG_RAX: 0000000000000078
RAX: ffffffffffffffda RBX: 0000000000003ffc RCX: 0000000000000000
RDX: 00000000200005c0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000012 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..

Reported-and-tested-by: syzbot+3286e58549edc479faae@syzkaller.appspotmail.com
Fixes: b3e5838252 ("clone: add CLONE_PIDFD")
Signed-off-by: Christian Brauner <christian@brauner.io>
2019-05-10 14:26:12 +02:00
..
bpf Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-05-07 22:03:58 -07:00
cgroup Merge branch 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2019-05-09 13:52:12 -07:00
configs
debug kdb: use bool for binary state indicators 2018-12-30 08:31:52 +00:00
dma DMA mapping updates for 5.2 2019-05-09 08:40:55 -07:00
events Printk changes for 5.2 2019-05-07 09:18:12 -07:00
gcov kernel/gcov/gcc_3_4.c: use struct_size() in kzalloc() 2019-03-07 18:32:02 -08:00
irq Driver core/kobject patches for 5.2-rc1 2019-05-07 13:01:40 -07:00
livepatch Driver core/kobject patches for 5.2-rc1 2019-05-07 13:01:40 -07:00
locking Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb()) 2019-05-06 16:57:52 -07:00
power Power management updates for 5.2-rc1 2019-05-06 19:40:31 -07:00
printk fbdev changes for v5.1: 2019-03-15 14:22:59 -07:00
rcu Printk changes for 5.2 2019-05-07 09:18:12 -07:00
sched Driver core/kobject patches for 5.2-rc1 2019-05-07 13:01:40 -07:00
time Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-05-07 22:03:58 -07:00
trace Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-05-07 22:03:58 -07:00
.gitignore Provide in-kernel headers to make extending kernel easier 2019-04-29 16:48:03 +02:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb()) 2019-05-06 16:57:52 -07:00
Kconfig.preempt
Makefile Driver core/kobject patches for 5.2-rc1 2019-05-07 13:01:40 -07:00
acct.c acct_on(): don't mess with freeze protection 2019-04-04 21:04:13 -04:00
async.c treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively 2019-04-09 14:19:06 +02:00
audit.c audit: connect LOGIN record to its syscall record 2019-03-20 20:57:48 -04:00
audit.h audit_compare_dname_path(): switch to const struct qstr * 2019-04-28 20:33:43 -04:00
audit_fsnotify.c audit_compare_dname_path(): switch to const struct qstr * 2019-04-28 20:33:43 -04:00
audit_tree.c fsnotify: switch send_to_group() and ->handle_event to const struct qstr * 2019-04-26 13:51:03 -04:00
audit_watch.c audit_compare_dname_path(): switch to const struct qstr * 2019-04-28 20:33:43 -04:00
auditfilter.c Merge branch 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-05-07 20:03:32 -07:00
auditsc.c Merge branch 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-05-07 20:03:32 -07:00
backtracetest.c backtrace-test: Simplify stack trace handling 2019-04-29 12:37:47 +02:00
bounds.c
capability.c LSM: add SafeSetID module that gates setid calls 2019-01-25 11:22:43 -08:00
compat.c time: make adjtime compat handling available for 32 bit 2019-02-07 00:13:27 +01:00
configs.c kernel/configs: use .incbin directive to embed config_data.gz 2019-03-07 18:32:02 -08:00
context_tracking.c
cpu.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 14:50:46 -07:00
cpu_pm.c
crash_core.c kexec: export PG_offline to VMCOREINFO 2019-03-05 21:07:14 -08:00
crash_dump.c
cred.c SELinux: Remove cred security blob poisoning 2019-01-08 13:18:44 -08:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c Merge branch 'for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2019-03-07 10:11:41 -08:00
extable.c
fail_function.c treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively 2019-04-09 14:19:06 +02:00
fork.c fork: do not release lock that wasn't taken 2019-05-10 14:26:12 +02:00
freezer.c
futex.c locking/futex: Allow low-level atomic operations to return -EAGAIN 2019-04-26 13:57:31 +01:00
gen_ikh_data.sh Provide in-kernel headers to make extending kernel easier 2019-04-29 16:48:03 +02:00
groups.c
hung_task.c kernel/hung_task.c: Use continuously blocked time when reporting. 2019-03-07 18:31:59 -08:00
iomem.c mm/resource: Use resource_overlaps() to simplify region_intersects() 2019-04-19 12:59:36 +02:00
irq_work.c irq_work: Do not raise an IPI when queueing work on the local CPU 2019-04-18 14:07:52 +02:00
jump_label.c locking/static_key: Don't take sleeping locks in __static_key_slow_dec_deferred() 2019-04-29 08:29:21 +02:00
kallsyms.c bpf: Add module name [bpf] to ksymbols for bpf programs 2019-01-21 17:38:56 -03:00
kcmp.c
kcov.c kcov: convert kcov.refcount to refcount_t 2019-03-07 18:32:02 -08:00
kexec.c
kexec_core.c power/suspend: Add function to disable secondaries for suspend 2019-05-03 19:42:41 +02:00
kexec_file.c crypto: shash - remove shash_desc::flags 2019-04-25 15:38:12 +08:00
kexec_internal.h
kheaders.c Provide in-kernel headers to make extending kernel easier 2019-04-29 16:48:03 +02:00
kmod.c
kprobes.c kprobes: Fix error check when reusing optimized probes 2019-04-16 09:38:16 +02:00
ksysfs.c
kthread.c Merge branch 'akpm' (patches from Andrew) 2019-03-06 10:31:36 -08:00
latencytop.c latency_top: Simplify stack trace handling 2019-04-29 12:37:48 +02:00
memremap.c mm/hmm: fix memremap.h, move dev_page_fault_t callback to hmm 2018-12-28 12:11:52 -08:00
module-internal.h
module.c Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-05-09 12:54:40 -07:00
module_signing.c
notifier.c
nsproxy.c
padata.c padata: Replace padata_attr_type default_attrs field with groups 2019-04-25 22:06:11 +02:00
panic.c s390: simplify disabled_wait 2019-05-02 13:54:11 +02:00
params.c
pid.c Fix failure path in alloc_pid() 2018-12-28 12:42:30 -08:00
pid_namespace.c
profile.c
ptrace.c ptrace: take into account saved_sigmask in PTRACE{GET,SET}SIGMASK 2019-03-29 10:01:37 -07:00
range.c
reboot.c
relay.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 13:27:20 -07:00
resource.c mm/resource: Use resource_overlaps() to simplify region_intersects() 2019-04-19 12:59:36 +02:00
rseq.c rseq: Remove superfluous rseq_len from task_struct 2019-04-19 12:39:32 +02:00
seccomp.c audit/stable-5.2 PR 20190507 2019-05-07 19:06:04 -07:00
signal.c Merge branch 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2019-05-09 13:52:12 -07:00
smp.c cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM 2019-01-30 19:27:00 +01:00
smpboot.c
smpboot.h
softirq.c softirq: Remove tasklet_hrtimer 2019-03-22 14:36:02 +01:00
stackleak.c
stacktrace.c stacktrace: Provide common infrastructure 2019-04-29 12:37:57 +02:00
stop_machine.c treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively 2019-04-09 14:19:06 +02:00
sys.c Merge branch 'akpm' (patches from Andrew) 2019-03-07 19:25:37 -08:00
sys_ni.c signal: support CLONE_PIDFD with pidfd_send_signal 2019-05-07 14:31:03 +02:00
sysctl.c ipv6: Add rate limit mask for ICMPv6 messages 2019-04-18 16:58:37 -07:00
sysctl_binary.c kernel/sysctl: add panic_print into sysctl 2019-01-04 13:13:47 -08:00
task_work.c
taskstats.c genetlink: optionally validate strictly/dumps 2019-04-27 17:07:22 -04:00
test_kprobes.c
torture.c torture: Don't try to offline the last CPU 2019-03-26 14:42:53 -07:00
tracepoint.c
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c umh: add exit routine for UMH process 2019-01-11 18:05:40 -08:00
up.c
user-return-notifier.c
user.c
user_namespace.c
utsname.c
utsname_sysctl.c
watchdog.c watchdog: Fix typo in comment 2019-04-18 14:05:51 +02:00
watchdog_hld.c kernel/watchdog_hld.c: hard lockup message should end with a newline 2019-04-19 09:46:05 -07:00
workqueue.c Merge branch 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2019-05-09 13:48:52 -07:00
workqueue_internal.h sched/core, workqueues: Distangle worker accounting from rq lock 2019-04-16 16:55:15 +02:00