Repository files (latest commit first)

Filename	Latest commit message	Latest commit date
Thomas Gleixner 1a1fb985f2 futex: Handle early deadlock return correctly ... commit 56222b212e ("futex: Drop hb->lock before enqueueing on the rtmutex") changed the locking rules in the futex code so that the hash bucket lock is not longer held while the waiter is enqueued into the rtmutex wait list. This made the lock and the unlock path symmetric, but unfortunately the possible early exit from __rt_mutex_proxy_start() due to a detected deadlock was not updated accordingly. That allows a concurrent unlocker to observe inconsitent state which triggers the warning in the unlock path. futex_lock_pi() futex_unlock_pi() lock(hb->lock) queue(hb_waiter) lock(hb->lock) lock(rtmutex->wait_lock) unlock(hb->lock) // acquired hb->lock hb_waiter = futex_top_waiter() lock(rtmutex->wait_lock) __rt_mutex_proxy_start() ---> fail remove(rtmutex_waiter); ---> returns -EDEADLOCK unlock(rtmutex->wait_lock) // acquired wait_lock wake_futex_pi() rt_mutex_next_owner() --> returns NULL --> WARN lock(hb->lock) unqueue(hb_waiter) The problem is caused by the remove(rtmutex_waiter) in the failure case of __rt_mutex_proxy_start() as this lets the unlocker observe a waiter in the hash bucket but no waiter on the rtmutex, i.e. inconsistent state. The original commit handles this correctly for the other early return cases (timeout, signal) by delaying the removal of the rtmutex waiter until the returning task reacquired the hash bucket lock. Treat the failure case of __rt_mutex_proxy_start() in the same way and let the existing cleanup code handle the eventual handover of the rtmutex gracefully. The regular rt_mutex_proxy_start() gains the rtmutex waiter removal for the failure case, so that the other callsites are still operating correctly. Add proper comments to the code so all these details are fully documented. Thanks to Peter for helping with the analysis and writing the really valuable code comments. Fixes: 56222b212e ("futex: Drop hb->lock before enqueueing on the rtmutex") Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com> Co-developed-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: linux-s390@vger.kernel.org Cc: Stefan Liebler <stli@linux.ibm.com> Cc: Sebastian Sewior <bigeasy@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1901292311410.1950@nanos.tec.linutronix.de		2019-02-08 13:00:36 +01:00
..
bpf	bpf: fix inner map masking to prevent oob under speculation	2019-01-18 15:19:56 -08:00
cgroup	Merge branch 'for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2018-12-29 10:57:20 -08:00
configs	kvm_config: add CONFIG_VIRTIO_MENU	2018-10-24 20:55:56 -04:00
debug	kdb: use bool for binary state indicators	2018-12-30 08:31:52 +00:00
dma	swiotlb: clear io_tlb_start and io_tlb_end in swiotlb_exit	2019-01-16 09:59:17 -05:00
events	perf core: Fix perf_proc_update_handler() bug	2019-01-18 11:10:38 -03:00
gcov
irq	genirq/irqdesc: Fix double increment in alloc_descs()	2019-01-18 00:43:09 +01:00
livepatch	livepatch: Replace synchronize_sched() with synchronize_rcu()	2018-12-01 12:38:50 -08:00
locking	futex: Handle early deadlock return correctly	2019-02-08 13:00:36 +01:00
power	mm: convert totalram_pages and totalhigh_pages variables to atomic	2018-12-28 12:11:47 -08:00
printk	Remove 'type' argument from access_ok() function	2019-01-03 18:57:57 -08:00
rcu	rcutorture: Don't do busted forward-progress testing	2018-12-01 12:45:42 -08:00
sched	Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-02-03 09:02:03 -08:00
time	posix-cpu-timers: Unbreak timer rearming	2019-01-15 16:34:37 +01:00
trace	tracing/uprobes: Fix output for multiple string arguments	2019-01-17 10:54:08 -05:00
.gitignore
acct.c
async.c
audit.c	audit: remove duplicated include from audit.c	2018-12-14 12:09:30 -05:00
audit.h	audit: use current whenever possible	2018-11-26 18:41:21 -05:00
audit_fsnotify.c	audit: minimize our use of audit_log_format()	2018-11-26 18:40:00 -05:00
audit_tree.c	audit: minimize our use of audit_log_format()	2018-11-26 18:40:00 -05:00
audit_watch.c	audit: minimize our use of audit_log_format()	2018-11-26 18:40:00 -05:00
auditfilter.c
auditsc.c	audit: use current whenever possible	2018-11-26 18:41:21 -05:00
backtracetest.c
bounds.c	kbuild: fix kernel/bounds.c 'W=1' warning	2018-10-31 08:54:14 -07:00
capability.c
compat.c	make 'user_access_begin()' do 'access_ok()'	2019-01-04 12:56:09 -08:00
configs.c
context_tracking.c
cpu.c	cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM	2019-01-30 19:27:00 +01:00
cpu_pm.c
crash_core.c	kernel/crash_core.c: print timestamp using time64_t	2018-08-22 10:52:47 -07:00
crash_dump.c
cred.c	cred: export get_task_cred().	2018-12-19 13:52:44 -05:00
delayacct.c	delayacct: track delays from thrashing cache pages	2018-10-26 16:26:32 -07:00
dma.c
elfcore.c
exec_domain.c
exit.c	kernel/exit.c: release ptraced tasks before zap_pid_ns_processes	2019-02-01 15:46:23 -08:00
extable.c
fail_function.c	kernel/fail_function.c: remove meaningless null pointer check before debugfs_remove_recursive	2018-10-31 08:54:12 -07:00
fork.c	Merge branch 'akpm' (patches from Andrew)	2019-01-08 18:58:29 -08:00
freezer.c	PM / reboot: Eliminate race between reboot and suspend	2018-08-06 12:35:20 +02:00
futex.c	futex: Handle early deadlock return correctly	2019-02-08 13:00:36 +01:00
groups.c
hung_task.c	kernel/hung_task.c: break RCU locks based on jiffies	2019-01-04 13:13:45 -08:00
iomem.c
irq_work.c
jump_label.c	jump_label: move 'asm goto' support test to Kconfig	2019-01-06 09:46:51 +09:00
kallsyms.c	kallsyms: reduce size a little on 64-bit	2018-09-10 22:54:33 +09:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt	kconfig: warn no new line at end of file	2018-12-15 17:44:35 +09:00
kcov.c	kernel/kcov.c: mark write_comp_data() as notrace	2019-01-04 13:13:47 -08:00
kexec.c	kexec: add call to LSM hook in original kexec_load syscall	2018-07-16 12:31:57 -07:00
kexec_core.c	mm: convert totalram_pages and totalhigh_pages variables to atomic	2018-12-28 12:11:47 -08:00
kexec_file.c	kexec_file: kexec_walk_memblock() only walks a dedicated region at kdump	2018-12-06 14:38:50 +00:00
kexec_internal.h
kmod.c
kprobes.c	Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-12-26 14:45:18 -08:00
ksysfs.c
kthread.c	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-08-13 11:25:07 -07:00
latencytop.c
Makefile	kbuild: change filechk to surround the given command with { }	2019-01-06 09:46:51 +09:00
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	modsign: log module name in the event of an error	2018-07-02 11:36:17 +02:00
module.c	jump_label: move 'asm goto' support test to Kconfig	2019-01-06 09:46:51 +09:00
module_signing.c	modsign: use all trusted keys to verify module signature	2018-11-07 14:41:41 +01:00
notifier.c
nsproxy.c
padata.c	padata: clean an indentation issue, remove extraneous space	2018-11-16 14:11:04 +08:00
panic.c	kernel/sysctl: add panic_print into sysctl	2019-01-04 13:13:47 -08:00
params.c
pid.c	Fix failure path in alloc_pid()	2018-12-28 12:42:30 -08:00
pid_namespace.c	signal: Use group_send_sig_info to kill all processes in a pid namespace	2018-09-16 16:08:25 +02:00
profile.c	mm: remove include/linux/bootmem.h	2018-10-31 08:54:16 -07:00
ptrace.c	Remove 'type' argument from access_ok() function	2019-01-03 18:57:57 -08:00
range.c
reboot.c	kernel/reboot.c: export pm_power_off_prepare	2018-09-11 16:13:24 +01:00
relay.c
resource.c	kernel, resource: check for IORESOURCE_SYSRAM in release_mem_region_adjustable	2018-12-28 12:11:49 -08:00
rseq.c	Remove 'type' argument from access_ok() function	2019-01-03 18:57:57 -08:00
seccomp.c	seccomp: fix UAF in user-trap code	2019-01-15 09:43:12 -08:00
signal.c	Remove 'type' argument from access_ok() function	2019-01-03 18:57:57 -08:00
smp.c	cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM	2019-01-30 19:27:00 +01:00
smpboot.c	smpboot: Remove cpumask from the API	2018-07-03 09:20:44 +02:00
smpboot.h
softirq.c	Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-10-25 11:43:47 -07:00
stackleak.c	stackleak: Mark stackleak_track_stack() as notrace	2018-12-05 19:31:44 -08:00
stacktrace.c
stop_machine.c	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-08-13 11:25:07 -07:00
sys.c	kernel/sys.c: Clarify that UNAME26 does not generate unique versions anymore	2019-01-14 10:38:03 +12:00
sys_ni.c	y2038: socket: Add compat_sys_recvmmsg_time64	2018-12-18 16:13:04 +01:00
sysctl.c	kernel/sysctl: add panic_print into sysctl	2019-01-04 13:13:47 -08:00
sysctl_binary.c	kernel/sysctl: add panic_print into sysctl	2019-01-04 13:13:47 -08:00
task_work.c
taskstats.c
test_kprobes.c
torture.c	torture: Remove unnecessary "ret" variables	2018-12-01 12:45:35 -08:00
tracepoint.c	tracing: Replace synchronize_sched() and call_rcu_sched()	2018-11-27 09:21:41 -08:00
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	smp,cpumask: introduce on_each_cpu_cond_mask	2018-10-09 16:51:11 +02:00
user-return-notifier.c
user.c	userns: use irqsave variant of refcount_dec_and_lock()	2018-08-22 10:52:47 -07:00
user_namespace.c	userns: also map extents in the reverse map to kernel IDs	2018-11-07 23:51:16 -06:00
utsname.c
utsname_sysctl.c	sys: don't hold uts_sem while accessing userspace memory	2018-08-11 02:05:53 -05:00
watchdog.c	watchdog: Mark watchdog touch functions as notrace	2018-08-30 12:56:40 +02:00
watchdog_hld.c	watchdog: Mark watchdog touch functions as notrace	2018-08-30 12:56:40 +02:00
workqueue.c	psi: fix aggregation idle shut-off	2019-02-01 15:46:23 -08:00
workqueue_internal.h	psi: fix aggregation idle shut-off	2019-02-01 15:46:23 -08:00