linux_dsm_epyc7002/kernel
Paul E. McKenney 35a35909ec rcu: Reject RCU_LOCKDEP_WARN() false positives
[ Upstream commit 3066820034b5dd4e89bd74a7739c51c2d6f5e554 ]

If another lockdep report runs concurrently with an RCU lockdep report
from RCU_LOCKDEP_WARN(), the following sequence of events can occur:

1.	debug_lockdep_rcu_enabled() sees that lockdep is enabled
	when called from (say) synchronize_rcu().

2.	Lockdep is disabled by a concurrent lockdep report.

3.	debug_lockdep_rcu_enabled() evaluates its lockdep-expression
	argument, for example, lock_is_held(&rcu_bh_lock_map).

4.	Because lockdep is now disabled, lock_is_held() plays it safe and
	returns the constant 1.

5.	But in this case, the constant 1 is not safe, because invoking
	synchronize_rcu() under rcu_read_lock_bh() is disallowed.

6.	debug_lockdep_rcu_enabled() wrongly invokes lockdep_rcu_suspicious(),
	resulting in a false-positive splat.

This commit therefore changes RCU_LOCKDEP_WARN() to check
debug_lockdep_rcu_enabled() after checking the lockdep expression,
so that any "safe" returns from lock_is_held() are rejected by
debug_lockdep_rcu_enabled().  This requires memory ordering, which is
supplied by READ_ONCE(debug_locks).  The resulting volatile accesses
prevent the compiler from reordering and the fact that only one variable
is being accessed prevents the underlying hardware from reordering.
The combination works for IA64, which can reorder reads to the same
location, but this is defeated by the volatile accesses, which compile
to load instructions that provide ordering.

Reported-by: syzbot+dde0cc33951735441301@syzkaller.appspotmail.com
Reported-by: Matthew Wilcox <willy@infradead.org>
Reported-by: syzbot+88e4f02896967fe1ab0d@syzkaller.appspotmail.com
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-20 16:05:38 +02:00
..
bpf bpf: Fix false positive kmemleak report in bpf_ringbuf_area_alloc() 2021-07-19 09:44:54 +02:00
cgroup cgroup: verify that source is a string 2021-07-20 16:05:36 +02:00
configs
debug
dma swiotlb: manipulate orig_addr when tlb_addr has offset 2021-06-30 08:47:29 -04:00
entry
events perf: Fix data race between pin_count increment/decrement 2021-06-16 12:01:45 +02:00
gcov gcov: re-fix clang-11+ support 2021-04-14 08:41:58 +02:00
irq genirq/matrix: Prevent allocation counter corruption 2021-05-11 14:47:17 +02:00
kcsan kcsan: Fix debugfs initcall return type 2021-05-26 12:06:54 +02:00
livepatch
locking lockdep: Fix wait-type for empty stack 2021-07-14 16:56:10 +02:00
power PM: EM: postpone creating the debugfs dir till fs_initcall 2021-03-30 14:32:04 +02:00
printk
rcu rcu: Reject RCU_LOCKDEP_WARN() false positives 2021-07-20 16:05:38 +02:00
sched rq-qos: fix missed wake-ups in rq_qos_throttle try two 2021-07-19 09:45:00 +02:00
time clocksource: Check per-CPU clock synchronization when marked unstable 2021-07-14 16:56:01 +02:00
trace tracing: Do not reference char * as a string in histograms 2021-07-20 16:05:36 +02:00
.gitignore kbuild: update config_data.gz only when the content of .config is changed 2021-05-11 14:47:37 +02:00
acct.c
async.c
audit_fsnotify.c
audit_tree.c
audit_watch.c
audit.c
audit.h
auditfilter.c
auditsc.c
backtracetest.c
bounds.c
capability.c
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c cpu/hotplug: Cure the cpusets trainwreck 2021-07-19 09:44:59 +02:00
crash_core.c crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo 2021-06-23 14:42:52 +02:00
crash_dump.c
cred.c cred: add missing return error code when set_cred_ucounts() failed 2021-07-14 16:56:55 +02:00
delayacct.c
dma.c
exec_domain.c
exit.c
extable.c
fail_function.c
fork.c sched/core: Initialize the idle task with preemption disabled 2021-07-14 16:55:50 +02:00
freezer.c Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing" 2021-04-07 15:00:14 +02:00
futex.c mm, futex: fix shared futex pgoff on shmem huge page 2021-06-30 08:47:29 -04:00
gen_kheaders.sh
groups.c
hung_task.c
iomem.c
irq_work.c
jump_label.c
kallsyms.c
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c
kexec_core.c
kexec_elf.c
kexec_file.c kernel: kexec_file: fix error return code of kexec_calculate_store_digests() 2021-05-19 10:13:09 +02:00
kexec_internal.h
kexec.c
kheaders.c
kmod.c
kprobes.c
ksysfs.c
kthread.c kthread_worker: fix return value when kthread_mod_delayed_work() races with kthread_cancel_delayed_work_sync() 2021-07-14 16:56:02 +02:00
latencytop.c
Makefile kbuild: update config_data.gz only when the content of .config is changed 2021-05-11 14:47:37 +02:00
module_signature.c
module_signing.c
module-internal.h
module.c module: limit enabling module.sig_enforce 2021-06-30 08:47:15 -04:00
notifier.c
nsproxy.c
padata.c
panic.c
params.c
pid_namespace.c
pid.c
profile.c
ptrace.c ptrace: make ptrace() fail if the tracee changed its pid unexpectedly 2021-05-26 12:06:49 +02:00
range.c
reboot.c
regset.c
relay.c
resource.c kernel/resource: make walk_mem_res() find all busy IORESOURCE_MEM resources 2021-05-19 10:13:09 +02:00
rseq.c
scftorture.c
scs.c
seccomp.c seccomp: Refactor notification handler to prepare for new semantics 2021-06-03 09:00:31 +02:00
signal.c
smp.c smp: Fix smp_call_function_single_async prototype 2021-05-14 09:50:46 +02:00
smpboot.c sched/core: Initialize the idle task with preemption disabled 2021-07-14 16:55:50 +02:00
smpboot.h
softirq.c
stackleak.c
stacktrace.c
static_call.c static_call: Align static_call_is_init() patching condition 2021-04-07 15:00:06 +02:00
stop_machine.c
sys_ni.c
sys.c Add a reference to ucounts for each cred 2021-07-14 16:55:48 +02:00
sysctl-test.c
sysctl.c
task_work.c
taskstats.c
test_kprobes.c
torture.c
tracepoint.c tracepoint: Add tracepoint_probe_register_may_exist() for BPF tracing 2021-07-14 16:55:46 +02:00
tsacct.c
ucount.c Add a reference to ucounts for each cred 2021-07-14 16:55:48 +02:00
uid16.c
uid16.h
umh.c
up.c smp: Fix smp_call_function_single_async prototype 2021-05-14 09:50:46 +02:00
user_namespace.c Add a reference to ucounts for each cred 2021-07-14 16:55:48 +02:00
user-return-notifier.c
user.c
usermode_driver.c
utsname_sysctl.c
utsname.c
watch_queue.c
watchdog_hld.c
watchdog.c watchdog: fix barriers when printing backtraces from all CPUs 2021-05-19 10:13:00 +02:00
workqueue_internal.h
workqueue.c wq: handle VM suspension in stall detection 2021-06-16 12:01:36 +02:00