Petr Mladek 03fc7f9c99 printk/nmi: Prevent deadlock when accessing the main log buffer in NMI ... The commit 719f6a7040 ("printk: Use the main logbuf in NMI when logbuf_lock is available") brought back the possible deadlocks in printk() and NMI. The check of logbuf_lock is done only in printk_nmi_enter() to prevent mixed output. But another CPU might take the lock later, enter NMI, and: + Both NMIs might be serialized by yet another lock, for example, the one in nmi_cpu_backtrace(). + The other CPU might get stopped in NMI, see smp_send_stop() in panic(). The only safe solution is to use trylock when storing the message into the main log-buffer. It might cause reordering when some lines go to the main lock buffer directly and others are delayed via the per-CPU buffer. It means that it is not useful in general. This patch replaces the problematic NMI deferred context with NMI direct context. It can be used to mark a code that might produce many messages in NMI and the risk of losing them is more critical than problems with eventual reordering. The context is then used when dumping trace buffers on oops. It was the primary motivation for the original fix. Also the reordering is even smaller issue there because some traces have their own time stamps. Finally, nmi_cpu_backtrace() need not longer be serialized because it will always us the per-CPU buffers again. Fixes: 719f6a7040 ("printk: Use the main logbuf in NMI when logbuf_lock is available") Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20180627142028.11259-1-pmladek@suse.com To: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>		2018-07-09 14:10:40 +02:00
..
bpf	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2018-05-25 19:54:42 -07:00
cgroup	Merge branch 'for-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2018-06-05 17:08:45 -07:00
configs	KVM changes for 4.16	2018-02-10 13:16:35 -08:00
debug	* Fix 2032 time access issues and new compiler warnings	2018-04-12 10:21:19 -07:00
events	perf/core: Wire up compat PERF_EVENT_IOC_QUERY_BPF, PERF_EVENT_IOC_MODIFY_ATTRIBUTES	2018-05-25 08:11:11 +02:00
gcov	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
irq	Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-06-04 19:59:22 -07:00
livepatch	livepatch: Allow to call a custom callback when freeing shadow variables	2018-04-17 13:42:48 +02:00
locking	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-06-04 16:40:11 -07:00
power	Power management updates for 4.18-rc1	2018-06-05 09:38:39 -07:00
printk	printk/nmi: Prevent deadlock when accessing the main log buffer in NMI	2018-07-09 14:10:40 +02:00
rcu	rcu/x86: Provide early rcu_cpu_starting() callback	2018-05-22 16:12:26 -07:00
sched	Power management updates for 4.18-rc1	2018-06-05 09:38:39 -07:00
time	Power management updates for 4.18-rc1	2018-06-05 09:38:39 -07:00
trace	printk/nmi: Prevent deadlock when accessing the main log buffer in NMI	2018-07-09 14:10:40 +02:00
.gitignore	…
Kconfig.freezer	…
Kconfig.hz	…
Kconfig.locks	…
Kconfig.preempt	…
Makefile	error-injection: Support fault injection framework	2018-01-12 17:33:38 -08:00
acct.c	kernel/acct.c: fix the acct->needcheck check in check_free_space()	2018-01-04 16:45:09 -08:00
async.c	kernel/async.c: revert "async: simplify lowest_in_progress()"	2018-02-06 18:32:44 -08:00
audit.c	audit/stable-4.17 PR 20180403	2018-04-06 15:01:25 -07:00
audit.h	audit: track the owner of the command mutex ourselves	2018-02-23 11:22:22 -05:00
audit_fsnotify.c	…
audit_tree.c	audit: track the owner of the command mutex ourselves	2018-02-23 11:22:22 -05:00
audit_watch.c	audit/stable-4.13 PR 20170816	2017-08-16 16:48:34 -07:00
auditfilter.c	audit: deprecate the AUDIT_FILTER_ENTRY filter	2018-02-15 14:36:29 -05:00
auditsc.c	audit: bail before bug check if audit disabled	2018-02-15 14:40:25 -05:00
backtracetest.c	…
bounds.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
capability.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
compat.c	Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-06-04 20:27:54 -07:00
configs.c	…
context_tracking.c	…
cpu.c	cpu/hotplug: Fix unused function warning	2018-03-15 20:34:40 +01:00
cpu_pm.c	PM / CPU: replace raw_notifier with atomic_notifier	2017-07-31 13:09:49 +02:00
crash_core.c	kexec: export PG_swapbacked to VMCOREINFO	2018-04-13 17:10:27 -07:00
crash_dump.c	…
cred.c	…
delayacct.c	delayacct: Use raw_spinlocks	2018-04-27 14:34:51 +02:00
dma.c	proc: introduce proc_create_single{,_data}	2018-05-16 07:23:35 +02:00
elfcore.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
exec_domain.c	proc: introduce proc_create_single{,_data}	2018-05-16 07:23:35 +02:00
exit.c	kernel: use kernel_wait4() instead of sys_wait4()	2018-04-02 20:14:51 +02:00
extable.c	extable: Make init_kernel_text() global	2018-02-21 16:54:06 +01:00
fail_function.c	error-injection: Fix to prohibit jump optimization	2018-03-12 16:16:00 +01:00
fork.c	fork: unconditionally clear stack on fork	2018-04-20 17:18:35 -07:00
freezer.c	…
futex.c	pids: introduce find_get_task_by_vpid() helper	2018-02-06 18:32:46 -08:00
futex_compat.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
groups.c	kernel: make groups_sort calling a responsibility group_info allocators	2017-12-14 16:00:49 -08:00
hung_task.c	…
irq_work.c	irq/work: Improve the flag definitions	2018-01-08 19:43:15 +01:00
jump_label.c	jump_label: Disable jump labels in __exit code	2018-03-20 08:57:17 +01:00
kallsyms.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk	2018-02-01 13:36:15 -08:00
kcmp.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
kcov.c	kcov: detect double association with a single task	2018-02-06 18:32:46 -08:00
kexec.c	kexec: call do_kexec_load() in compat syscall directly	2018-04-02 20:15:01 +02:00
kexec_core.c	x86/mm, kexec: Allow kexec to be used with SME	2017-07-18 11:38:04 +02:00
kexec_file.c	kernel/kexec_file.c: allow archs to set purgatory load address	2018-04-13 17:10:28 -07:00
kexec_internal.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
kmod.c	kmod: move #ifdef CONFIG_MODULES wrapper to Makefile	2017-09-08 18:26:51 -07:00
kprobes.c	kprobes: Fix random address output of blacklist file	2018-04-25 10:27:56 -04:00
ksysfs.c	kexec: move vmcoreinfo out of the kernel's .bss section	2017-07-12 16:25:59 -07:00
kthread.c	kthread: Allow kthread_park() on a parked kthread	2018-05-25 08:03:51 +02:00
latencytop.c	…
memremap.c	kernel/memremap: Remove stale devres_free() call	2018-03-06 10:58:54 -08:00
module-internal.h	…
module.c	init: fix false positives in W+X checking	2018-05-11 17:28:45 -07:00
module_signing.c	…
notifier.c	…
nsproxy.c	…
padata.c	padata: add SPDX identifier	2018-01-05 18:43:00 +11:00
panic.c	taint: add taint for randstruct	2018-04-11 10:28:35 -07:00
params.c	kernel/params.c: downgrade warning for unsafe parameters	2018-04-11 10:28:37 -07:00
pid.c	xarray: add the xa_lock to the radix_tree_root	2018-04-11 10:28:39 -07:00
pid_namespace.c	Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2018-04-03 19:15:32 -07:00
profile.c	…
ptrace.c	pids: introduce find_get_task_by_vpid() helper	2018-02-06 18:32:46 -08:00
range.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
reboot.c	kernel/reboot.c: add devm_register_reboot_notifier()	2017-11-17 16:10:04 -08:00
relay.c	kernel/relay.c: limit kmalloc size to KMALLOC_MAX_SIZE	2018-02-21 15:35:43 -08:00
resource.c	resource: switch to proc_create_seq_data	2018-05-16 07:24:30 +02:00
seccomp.c	seccomp: Move speculation migitation control to arch code	2018-05-05 00:51:44 +02:00
signal.c	Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2018-06-04 15:23:48 -07:00
smp.c	smp/core: Use lockdep to assert IRQs are disabled/enabled	2017-11-08 11:13:50 +01:00
smpboot.c	watchdog/core, powerpc: Lock cpus across reconfiguration	2017-10-04 10:53:54 +02:00
smpboot.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
softirq.c	Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-06-04 19:59:22 -07:00
stacktrace.c	…
stop_machine.c	Linux 4.17-rc5	2018-05-15 08:10:50 +02:00
sys.c	kernel/sys.c: fix potential Spectre v1 issue	2018-05-25 18:12:11 -07:00
sys_ni.c	aio: implement io_pgetevents	2018-05-02 19:57:24 +02:00
sysctl.c	kernel/sysctl.c: add kdoc comments to do_proc_do{u}intvec_minmax_conv_param	2018-04-11 10:28:38 -07:00
sysctl_binary.c	staging: irda: remove remaining remants of irda code removal	2018-04-16 11:26:49 +02:00
task_work.c	locking/barriers: Convert users of lockless_dereference() to READ_ONCE()	2017-12-17 13:57:15 +01:00
taskstats.c	pids: introduce find_get_task_by_vpid() helper	2018-02-06 18:32:46 -08:00
test_kprobes.c	kprobes: Disable the jprobes test code	2017-10-20 11:02:54 +02:00
torture.c	rcu: Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs()	2018-05-15 10:27:29 -07:00
tracepoint.c	tracepoint: Do not warn on ENOMEM	2018-04-30 12:09:56 -04:00
tsacct.c	…
ucount.c	headers: untangle kmemleak.h from mm.h	2018-04-05 21:36:27 -07:00
uid16.c	fs: add do_fchownat(), ksys_fchown() helpers and ksys_{,l}chown() wrappers	2018-04-02 20:15:59 +02:00
uid16.h	kernel: provide ksys_*() wrappers for syscalls called by kernel/uid16.c	2018-04-02 20:15:30 +02:00
umh.c	kernel: use kernel_wait4() instead of sys_wait4()	2018-04-02 20:14:51 +02:00
up.c	smp: Avoid using two cache lines for struct call_single_data	2017-08-29 15:14:38 +02:00
user-return-notifier.c	…
user.c	efivarfs: Limit the rate for non-root to read files	2018-02-22 10:21:02 -08:00
user_namespace.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2017-11-16 12:20:15 -08:00
utsname.c	uts: create "struct uts_namespace" from kmem_cache	2018-04-11 10:28:35 -07:00
utsname_sysctl.c	…
watchdog.c	Merge branch 'linus' into sched/core, to pick up fixes	2017-11-08 10:17:15 +01:00
watchdog_hld.c	Merge branch 'linus' into core/urgent, to pick up dependent commits	2017-11-04 08:53:04 +01:00
workqueue.c	workqueue: move function definitions within CONFIG_SMP block	2018-05-23 11:16:58 -07:00
workqueue_internal.h	workqueue: Set worker->desc to workqueue name by default	2018-05-18 08:47:13 -07:00