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89e9e66ba1
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Sebastian Andrzej Siewior 89e9e66ba1 futex: Handle unlock_pi race gracefully 
If userspace calls UNLOCK_PI unconditionally without trying the TID -> 0
transition in user space first then the user space value might not have the
waiters bit set. This opens the following race:

CPU0	    	      	    CPU1
uval = get_user(futex)
			    lock(hb)
lock(hb)
			    futex |= FUTEX_WAITERS
			    ....
			    unlock(hb)

cmpxchg(futex, uval, newval)

So the cmpxchg fails and returns -EINVAL to user space, which is wrong because
the futex value is valid.

To handle this (yes, yet another) corner case gracefully, check for a flag
change and retry.

[ tglx: Massaged changelog and slightly reworked implementation ]

Fixes: ccf9e6a80d ("futex: Make unlock_pi more robust")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1460723739-5195-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-04-20 12:33:13 +02:00
..
bpf bpf: add missing map_flags to bpf_map_show_fdinfo 2016-03-25 11:36:41 -04:00
configs
debug mm/init: Add 'rodata=off' boot cmdline parameter to disable read-only kernel mappings 2016-02-22 08:51:37 +01:00
events Merge branch 'PAGE_CACHE_SIZE-removal' 2016-04-04 10:50:24 -07:00
gcov gcov: use within_module() helper. 2015-12-04 22:46:25 +01:00
irq kernel/...: convert pr_warning to pr_warn 2016-03-22 15:36:02 -07:00
livepatch livepatch/module: remove livepatch module notifier 2016-03-17 09:45:10 +01:00
locking locking/pvqspinlock: Fix division by zero in qstat_read() 2016-04-19 10:49:19 +02:00
power Power management and ACPI material for v4.6-rc1, part 2 2016-03-24 22:59:58 -07:00
printk printk: add clear_idx symbol to vmcoreinfo 2016-03-17 15:09:34 -07:00
rcu kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
sched locking/atomic, sched: Unexport fetch_or() 2016-03-29 11:52:11 +02:00
time timers/nohz: Convert tick dependency mask to atomic_t 2016-03-29 11:52:11 +02:00
trace arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
.gitignore certs: add .gitignore to stop git nagging about x509_certificate_list 2015-10-21 15:18:35 +01:00
acct.c
async.c async: export current_is_async() 2015-11-19 17:51:48 +01:00
audit_fsnotify.c wrappers for ->i_mutex access 2016-01-22 18:04:28 -05:00
audit_tree.c audit: audit_tree_match can be boolean 2015-11-04 08:23:51 -05:00
audit_watch.c Merge branch 'stable-4.6' of git://git.infradead.org/users/pcmoore/audit 2016-03-19 17:52:49 -07:00
audit.c Merge branch 'stable-4.6' of git://git.infradead.org/users/pcmoore/audit 2016-03-19 17:52:49 -07:00
audit.h security: Make inode argument of inode_getsecid non-const 2015-12-24 11:09:39 -05:00
auditfilter.c audit: Fix typo in comment 2016-02-08 11:25:39 -05:00
auditsc.c auditsc: for seccomp events, log syscall compat state using in_compat_syscall 2016-03-22 15:36:02 -07:00
backtracetest.c
bounds.c
capability.c
cgroup_freezer.c cgroup: kill cgrp_ss_priv[CGROUP_CANFORK_COUNT] and friends 2015-12-03 10:24:08 -05:00
cgroup_pids.c cgroup_pids: fix a typo. 2015-12-14 14:54:37 -05:00
cgroup.c Merge branch 'for-4.6-ns' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2016-03-21 10:05:13 -07:00
compat.c
configs.c
context_tracking.c context_tracking: Switch to new static_branch API 2015-11-24 09:56:43 +01:00
cpu_pm.c kernel/cpu_pm: fix cpu_cluster_pm_exit comment 2015-09-03 02:42:20 +02:00
cpu.c cpu/hotplug: Document states better 2016-03-12 20:57:38 +01:00
cpuset.c Merge branch 'for-4.6-ns' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2016-03-21 10:05:13 -07:00
crash_dump.c
cred.c kmemcg: account certain kmem allocations to memcg 2016-01-14 16:00:49 -08:00
delayacct.c kmemcg: account certain kmem allocations to memcg 2016-01-14 16:00:49 -08:00
dma.c
elfcore.c
exec_domain.c
exit.c oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space 2016-03-25 16:37:42 -07:00
extable.c kernel/extable.c: remove duplicated include 2015-09-10 13:29:01 -07:00
fork.c kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
freezer.c
futex_compat.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-01-20 17:09:18 -08:00
futex.c futex: Handle unlock_pi race gracefully 2016-04-20 12:33:13 +02:00
groups.c
hung_task.c kernel/hung_task.c: use timeout diff when timeout is updated 2016-03-22 15:36:02 -07:00
irq_work.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
jump_label.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
kallsyms.c kallsyms: add support for relative offsets in kallsyms address table 2016-03-15 16:55:16 -07:00
kcmp.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-01-20 17:09:18 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
kexec_core.c kexec: Set IORESOURCE_SYSTEM_RAM for System RAM 2016-01-30 09:49:57 +01:00
kexec_file.c Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2016-03-17 11:33:45 -07:00
kexec_internal.h kexec: move some memembers and definitions within the scope of CONFIG_KEXEC_FILE 2016-01-20 17:09:18 -08:00
kexec.c kexec: set KEXEC_TYPE_CRASH before sanity_check_segment_list() 2016-01-20 17:09:18 -08:00
kmod.c kmod: don't run async usermode helper as a child of kworker thread 2015-10-23 17:55:10 +09:00
kprobes.c perf/x86/hw_breakpoints: Disallow kernel breakpoints unless kprobe-safe 2015-08-04 10:16:54 +02:00
ksysfs.c rcu: Remove TINY_RCU bloat from pointless boot parameters 2015-12-07 16:59:37 -08:00
kthread.c kernel/kthread.c:kthread_create_on_node(): clarify documentation 2015-09-04 16:54:41 -07:00
latencytop.c sched/debug: Make schedstats a runtime tunable that is disabled by default 2016-02-09 11:54:23 +01:00
Makefile kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
membarrier.c sys_membarrier(): system-wide memory barrier (generic, x86) 2015-09-11 15:21:34 -07:00
memremap.c memremap: add MEMREMAP_WC flag 2016-03-22 15:36:02 -07:00
module_signing.c X.509: Make algo identifiers text instead of enum 2016-03-03 21:49:27 +00:00
module-internal.h
module.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching 2016-03-17 21:46:32 -07:00
notifier.c Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-09-01 08:40:25 -07:00
nsproxy.c cgroup: introduce cgroup namespaces 2016-02-16 13:04:58 -05:00
padata.c
panic.c panic: change nmi_panic from macro to function 2016-03-22 15:36:02 -07:00
params.c Nothing exciting, minor tweaks and cleanups. 2015-11-09 15:53:39 -08:00
pid_namespace.c
pid.c Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-01-31 15:44:04 -08:00
profile.c profile: hide unused functions when !CONFIG_PROC_FS 2016-03-22 15:36:02 -07:00
ptrace.c ptrace: change __ptrace_unlink() to clear ->ptrace under ->siglock 2016-03-22 15:36:02 -07:00
range.c
reboot.c kexec: split kexec_load syscall from kexec core code 2015-09-10 13:29:01 -07:00
relay.c wrappers for ->i_mutex access 2016-01-22 18:04:28 -05:00
resource.c /proc/iomem: only expose physical resource addresses to privileged users 2016-04-14 12:56:09 -07:00
seccomp.c seccomp: check in_compat_syscall, not is_compat_task, in strict mode 2016-03-22 15:36:02 -07:00
signal.c kernel/signal.c: add compile-time check for __ARCH_SI_PREAMBLE_SIZE 2016-03-22 15:36:02 -07:00
smp.c Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-03-15 13:50:29 -07:00
smpboot.c cpu/hotplug: Unpark smpboot threads from the state machine 2016-03-01 20:36:56 +01:00
smpboot.h cpu/hotplug: Create hotplug threads 2016-03-01 20:36:56 +01:00
softirq.c arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
stacktrace.c
stop_machine.c kernel/stop_machine.c: remove CONFIG_SMP dependencies 2016-01-16 11:17:24 -08:00
sys_ni.c vfs: add copy_file_range syscall and vfs helper 2015-12-01 14:00:53 -05:00
sys.c timer: convert timer_slack_ns from unsigned long to u64 2016-03-17 15:09:34 -07:00
sysctl_binary.c fs/coredump: prevent fsuid=0 dumps into user-controlled directories 2016-03-22 15:36:02 -07:00
sysctl.c mm: scale kswapd watermarks in proportion to memory 2016-03-17 15:09:34 -07:00
task_work.c task_work: remove fifo ordering guarantee 2015-09-05 13:46:58 -07:00
taskstats.c
test_kprobes.c
torture.c torture: Consolidate cond_resched_rcu_qs() into stutter_wait() 2015-10-06 11:25:01 -07:00
tracepoint.c kernel/...: convert pr_warning to pr_warn 2016-03-22 15:36:02 -07:00
tsacct.c time, acct: Drop irq save & restore from __acct_update_integrals() 2016-02-29 09:53:09 +01:00
uid16.c
up.c
user_namespace.c kernel/*: switch to memdup_user_nul() 2016-01-04 10:27:55 -05:00
user-return-notifier.c
user.c
utsname_sysctl.c
utsname.c
watchdog.c watchdog: don't run proc_watchdog_update if new value is same as old 2016-03-17 15:09:34 -07:00
workqueue_internal.h sched/core: Get rid of 'cpu' argument in wq_worker_sleeping() 2016-03-02 10:28:47 -05:00
workqueue.c Merge branch 'for-4.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2016-03-18 20:05:39 -07:00