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Steven Rostedt (Google) 14b7965728 ring-buffer: Fix a race in rb_time_cmpxchg() for 32 bit archs 
commit fff88fa0fbc7067ba46dde570912d63da42c59a9 upstream.

Mathieu Desnoyers pointed out an issue in the rb_time_cmpxchg() for 32 bit
architectures. That is:

 static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
 {
	unsigned long cnt, top, bottom, msb;
	unsigned long cnt2, top2, bottom2, msb2;
	u64 val;

	/* The cmpxchg always fails if it interrupted an update */
	 if (!__rb_time_read(t, &val, &cnt2))
		 return false;

	 if (val != expect)
		 return false;

<<<< interrupted here!

	 cnt = local_read(&t->cnt);

The problem is that the synchronization counter in the rb_time_t is read
*after* the value of the timestamp is read. That means if an interrupt
were to come in between the value being read and the counter being read,
it can change the value and the counter and the interrupted process would
be clueless about it!

The counter needs to be read first and then the value. That way it is easy
to tell if the value is stale or not. If the counter hasn't been updated,
then the value is still good.

Link: https://lore.kernel.org/linux-trace-kernel/20231211201324.652870-1-mathieu.desnoyers@efficios.com/
Link: https://lore.kernel.org/linux-trace-kernel/20231212115301.7a9c9a64@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Fixes: 10464b4aa605e ("ring-buffer: Add rb_time_t 64 bit operations for speeding up 32 bit")
Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-11-18 12:11:57 +01:00
..
bpf bpf: Fix precision tracking for BPF_ALU | BPF_TO_BE | BPF_END 2024-11-18 11:43:21 +01:00
cgroup cgroup: Remove duplicates in cgroup v1 tasks file 2024-11-08 11:25:51 +01:00
configs Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
debug kgdb: Flush console before entering kgdb on panic 2024-11-18 11:43:15 +01:00
dma Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
entry Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
events perf: Fix perf_event_validate_size() lockdep splat 2024-11-18 12:11:57 +01:00
futex futex: Don't include process MM in futex key on no-MMU 2024-11-18 11:42:47 +01:00
gcov Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq genirq/generic_chip: Make irq_remove_generic_chip() irqdomain aware 2024-11-18 11:43:25 +01:00
kcsan Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
livepatch livepatch: Fix missing newline character in klp_resolve_symbols() 2024-11-18 11:43:05 +01:00
locking lockdep: Fix block chain corruption 2024-11-18 12:10:56 +01:00
power PM: hibernate: Clean up sync_read handling in snapshot_write_next() 2024-11-18 11:43:24 +01:00
printk printk: Don't allow userspace to write to /dev/kmsg 2024-11-17 17:43:00 +01:00
rcu rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects 2024-11-18 11:43:24 +01:00
sched Revert "kernel: ems/ego: Allow CPU frequency changes to be amended before they're set" 2024-11-18 07:48:15 +01:00
time Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
trace ring-buffer: Fix a race in rb_time_cmpxchg() for 32 bit archs 2024-11-18 12:11:57 +01:00
acct.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
async.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit_fsnotify.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit_tree.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit_watch.c audit: don't WARN_ON_ONCE(!current->mm) in audit_exe_compare() 2024-11-18 11:43:21 +01:00
auditfilter.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
auditsc.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
backtracetest.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
bounds.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
capability.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cfi.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
compat.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
configs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
context_tracking.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpu.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpu_pm.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_core.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_dump.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cred.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
delayacct.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
dma.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
exec_domain.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
exit.c security: samsung: defex_lsm: nuke 2024-06-15 16:20:49 -03:00
extable.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
fail_function.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
fork.c security: samsung: defex_lsm: nuke 2024-06-15 16:20:49 -03:00
freezer.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
gen_kheaders.sh Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
groups.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
hung_task.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
iomem.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq_work.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
jump_label.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kallsyms.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kcmp.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.freezer Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.hz Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.locks Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.preempt Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kcov.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_core.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_elf.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_file.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_internal.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kheaders.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kmod.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kprobes.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ksysfs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kthread.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
latencytop.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Makefile kernel: Use the stock defconfig for /proc/config.gz 2024-06-15 16:20:14 -03:00
module-internal.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
module.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
module_signature.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
module_signing.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
notifier.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
nsproxy.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
padata.c crypto: pcrypt - Fix hungtask for PADATA_RESET 2024-11-18 11:43:13 +01:00
panic.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
params.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pid.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pid_namespace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
profile.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ptrace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
range.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
reboot.c kernel/reboot: emergency_restart: Set correct system_state 2024-11-18 11:43:25 +01:00
regset.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
relay.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
resource.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
rseq.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
scftorture.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
scs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
seccomp.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
signal.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smp.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smpboot.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smpboot.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
softirq.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stackleak.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stacktrace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
static_call.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stop_machine.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sys.c f2fs: Add support for reporting a fake kernel version to fsck 2024-11-17 17:43:26 +01:00
sys_ni.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sysctl-test.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sysctl.c drivers: usb: add toggle for disabling newly added USB devices 2024-10-04 20:09:29 -03:00
task_work.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
taskstats.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
test_kprobes.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
torture.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tracepoint.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tsacct.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ucount.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
uid16.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
uid16.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
umh.c security: samsung: defex_lsm: nuke 2024-06-15 16:20:49 -03:00
up.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
user-return-notifier.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
user.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
user_namespace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
usermode_driver.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
utsname.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
utsname_sysctl.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
watch_queue.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
watchdog.c watchdog: move softlockup_panic back to early_param 2024-11-18 11:43:21 +01:00
watchdog_hld.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
workqueue.c Revert "workqueue: remove unused cancel_work()" 2024-11-18 12:11:11 +01:00
workqueue_internal.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00