linux/kernel
Steven Rostedt (Google) 529f020f7b ring-buffer: Do not try to put back write_stamp
commit dd93942570 upstream.

If an update to an event is interrupted by another event between the time
the initial event allocated its buffer and where it wrote to the
write_stamp, the code try to reset the write stamp back to the what it had
just overwritten. It knows that it was overwritten via checking the
before_stamp, and if it didn't match what it wrote to the before_stamp
before it allocated its space, it knows it was overwritten.

To put back the write_stamp, it uses the before_stamp it read. The problem
here is that by writing the before_stamp to the write_stamp it makes the
two equal again, which means that the write_stamp can be considered valid
as the last timestamp written to the ring buffer. But this is not
necessarily true. The event that interrupted the event could have been
interrupted in a way that it was interrupted as well, and can end up
leaving with an invalid write_stamp. But if this happens and returns to
this context that uses the before_stamp to update the write_stamp again,
it can possibly incorrectly make it valid, causing later events to have in
correct time stamps.

As it is OK to leave this function with an invalid write_stamp (one that
doesn't match the before_stamp), there's no reason to try to make it valid
again in this case. If this race happens, then just leave with the invalid
write_stamp and the next event to come along will just add a absolute
timestamp and validate everything again.

Bonus points: This gets rid of another cmpxchg64!

Link: https://lore.kernel.org/linux-trace-kernel/20231214222921.193037a7@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Fixes: a389d86f7f ("ring-buffer: Have nested events still record running time stamp")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-12-20 15:17:42 +01:00
..
bpf bpf: Fix precision tracking for BPF_ALU | BPF_TO_BE | BPF_END 2023-11-28 16:56:27 +00:00
cgroup cgroup: Remove duplicates in cgroup v1 tasks file 2023-10-19 23:05:37 +02:00
configs drivers/char: remove /dev/kmem for good 2021-05-07 00:26:34 -07:00
debug kgdb: Flush console before entering kgdb on panic 2023-11-28 16:56:20 +00:00
dma dma-debug: don't call __dma_entry_alloc_check_leak() under free_entries_lock 2023-10-06 13:18:14 +02:00
entry entry/rcu: Check TIF_RESCHED _after_ delayed RCU wake-up 2023-03-30 12:47:51 +02:00
events perf: Fix perf_event_validate_size() lockdep splat 2023-12-20 15:17:41 +01:00
futex futex: Don't include process MM in futex key on no-MMU 2023-11-20 11:08:13 +01:00
gcov gcov: add support for checksum field 2022-12-31 13:14:47 +01:00
irq genirq/generic_chip: Make irq_remove_generic_chip() irqdomain aware 2023-11-28 16:56:30 +00:00
kcsan kcsan: Don't expect 64 bits atomic builtins from 32 bits architectures 2023-07-23 13:47:12 +02:00
livepatch livepatch: Fix missing newline character in klp_resolve_symbols() 2023-11-20 11:08:25 +01:00
locking lockdep: Fix block chain corruption 2023-12-03 07:31:23 +01:00
power PM: hibernate: Clean up sync_read handling in snapshot_write_next() 2023-11-28 16:56:29 +00:00
printk printk: Consolidate console deferred printing 2023-09-23 11:09:59 +02:00
rcu rcu: Avoid tracing a few functions executed in stop machine 2023-12-08 08:48:02 +01:00
sched sched: Fix stop_one_cpu_nowait() vs hotplug 2023-11-20 11:08:13 +01:00
time hrtimers: Push pending hrtimers away from outgoing CPU earlier 2023-12-13 18:36:31 +01:00
trace ring-buffer: Do not try to put back write_stamp 2023-12-20 15:17:42 +01:00
.gitignore .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
acct.c acct: fix potential integer overflow in encode_comp_t() 2022-12-31 13:14:40 +01:00
async.c Revert "module, async: async_synchronize_full() on module init iff async is used" 2022-02-23 12:03:07 +01:00
audit_fsnotify.c audit: fix potential double free on error path from fsnotify_add_inode_mark 2022-08-31 17:16:33 +02:00
audit_tree.c audit: move put_tree() to avoid trim_trees refcount underflow and UAF 2021-08-24 18:52:36 -04:00
audit_watch.c audit: don't WARN_ON_ONCE(!current->mm) in audit_exe_compare() 2023-11-28 16:56:27 +00:00
audit.c audit: improve audit queue handling when "audit=1" on cmdline 2022-02-08 18:34:03 +01:00
audit.h audit: log AUDIT_TIME_* records only from rules 2022-04-08 14:23:06 +02:00
auditfilter.c
auditsc.c audit: fix possible soft lockup in __audit_inode_child() 2023-09-19 12:22:39 +02:00
backtracetest.c
bounds.c
capability.c
cfi.c cfi: Fix __cfi_slowpath_diag RCU usage with cpuidle 2022-06-22 14:22:04 +02:00
compat.c sched_getaffinity: don't assume 'cpumask_size()' is fully initialized 2023-04-05 11:24:53 +02:00
configs.c
context_tracking.c
cpu_pm.c PM: cpu: Make notifier chain use a raw_spinlock_t 2021-08-16 18:55:32 +02:00
cpu.c hrtimers: Push pending hrtimers away from outgoing CPU earlier 2023-12-13 18:36:31 +01:00
crash_core.c kernel/crash_core: suppress unknown crashkernel parameter warning 2021-12-29 12:28:49 +01:00
crash_dump.c
cred.c cred: switch to using atomic_long_t 2023-12-20 15:17:37 +01:00
delayacct.c delayacct: Add sysctl to enable at runtime 2021-05-12 11:43:25 +02:00
dma.c
exec_domain.c
exit.c exit: Use READ_ONCE() for all oops/warn limit reads 2023-02-01 08:27:22 +01:00
extable.c
fail_function.c kernel/fail_function: fix memory leak with using debugfs_lookup() 2023-03-11 13:57:38 +01:00
fork.c kernel/fork: beware of __put_task_struct() calling context 2023-09-23 11:09:55 +02:00
freezer.c sched: Add get_current_state() 2021-06-18 11:43:08 +02:00
gen_kheaders.sh kbuild: clean up ${quiet} checks in shell scripts 2021-05-27 04:01:50 +09:00
groups.c
hung_task.c Merge branch 'akpm' (patches from Andrew) 2021-07-02 12:08:10 -07:00
iomem.c
irq_work.c irq_work: Make irq_work_queue() NMI-safe again 2021-06-10 10:00:08 +02:00
jump_label.c jump_label: Fix jump_label_text_reserved() vs __init 2021-07-05 10:46:20 +02:00
kallsyms.c kallsyms: Make kallsyms_on_each_symbol generally available 2023-12-13 18:36:45 +01:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/rwlock: Provide RT variant 2021-08-17 17:50:51 +02:00
Kconfig.preempt sched/core: Disable CONFIG_SCHED_CORE by default 2021-06-28 22:43:05 +02:00
kcov.c
kexec_core.c kexec: fix a memory leak in crash_shrink_memory() 2023-07-23 13:46:52 +02:00
kexec_elf.c
kexec_file.c kexec: support purgatories with .text.hot sections 2023-06-21 15:59:14 +02:00
kexec_internal.h panic, kexec: make __crash_kexec() NMI safe 2023-04-20 12:13:57 +02:00
kexec.c kernel: kexec: copy user-array safely 2023-11-28 16:56:16 +00:00
kheaders.c kheaders: Use array declaration instead of char 2023-05-11 23:00:17 +09:00
kmod.c modules: add CONFIG_MODPROBE_PATH 2021-05-07 00:26:33 -07:00
kprobes.c kprobes: consistent rcu api usage for kretprobe holder 2023-12-13 18:36:42 +01:00
ksysfs.c kexec: turn all kexec_mutex acquisitions into trylocks 2023-04-20 12:13:57 +02:00
kthread.c kthread: add the helper function kthread_run_on_cpu() 2023-03-30 12:47:42 +02:00
latencytop.c
Makefile futex: Move to kernel/futex/ 2022-12-31 13:14:04 +01:00
module_signature.c
module_signing.c
module-internal.h
module.c modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules 2023-09-06 21:28:38 +01:00
notifier.c notifier: Remove atomic_notifier_call_chain_robust() 2021-08-16 18:55:32 +02:00
nsproxy.c memcg: enable accounting for new namesapces and struct nsproxy 2021-09-03 09:58:12 -07:00
padata.c crypto: pcrypt - Fix hungtask for PADATA_RESET 2023-11-28 16:56:18 +00:00
panic.c exit: Use READ_ONCE() for all oops/warn limit reads 2023-02-01 08:27:22 +01:00
params.c params: lift param_set_uint_minmax to common code 2021-08-16 14:42:22 +02:00
pid_namespace.c rcu-tasks: Fix synchronize_rcu_tasks() VS zap_pid_ns_processes() 2023-03-10 09:39:09 +01:00
pid.c kernel/pid.c: implement additional checks upon pidfd_create() parameters 2021-08-10 12:53:07 +02:00
profile.c profiling: fix shift too large makes kernel panic 2022-08-17 14:24:04 +02:00
ptrace.c ptrace: Reimplement PTRACE_KILL by always sending SIGKILL 2022-06-09 10:22:29 +02:00
range.c
reboot.c kernel/reboot: emergency_restart: Set correct system_state 2023-11-28 16:56:31 +00:00
regset.c
relay.c relayfs: fix out-of-bounds access in relay_file_read 2023-05-11 23:00:18 +09:00
resource_kunit.c
resource.c dax/kmem: Fix leak of memory-hotplug resources 2023-03-10 09:40:08 +01:00
rseq.c rseq: Remove broken uapi field layout on 32-bit little endian 2022-04-08 14:23:10 +02:00
scftorture.c scftorture: Forgive memory-allocation failure if KASAN 2023-09-23 11:09:55 +02:00
scs.c scs: Release kasan vmalloc poison in scs_free process 2021-11-18 19:16:29 +01:00
seccomp.c seccomp: Invalidate seccomp mode to catch death failures 2022-02-16 12:56:38 +01:00
signal.c signal handling: don't use BUG_ON() for debugging 2022-07-21 21:24:42 +02:00
smp.c locking/csd_lock: Change csdlock_debug from early_param to __setup 2022-08-17 14:24:24 +02:00
smpboot.c smpboot: Replace deprecated CPU-hotplug functions. 2021-08-10 14:57:42 +02:00
smpboot.h
softirq.c timers/nohz: Last resort update jiffies on nohz_full IRQ entry 2023-08-16 18:22:04 +02:00
stackleak.c gcc-plugins/stackleak: Use noinstr in favor of notrace 2022-02-23 12:03:07 +01:00
stacktrace.c stacktrace: move filter_irq_stacks() to kernel/stacktrace.c 2022-04-13 20:59:28 +02:00
static_call_inline.c static_call: Don't make __static_call_return0 static 2022-04-13 20:59:28 +02:00
static_call.c static_call: Don't make __static_call_return0 static 2022-04-13 20:59:28 +02:00
stop_machine.c
sys_ni.c kernel/sys_ni: add compat entry for fadvise64_64 2022-08-31 17:16:33 +02:00
sys.c kernel/sys.c: fix and improve control flow in __sys_setres[ug]id() 2023-04-26 13:51:52 +02:00
sysctl-test.c kernel/sysctl-test: Remove some casts which are no-longer required 2021-06-23 16:41:24 -06:00
sysctl.c kernel/panic: move panic sysctls to its own file 2023-02-01 08:27:20 +01:00
task_work.c kasan: record task_work_add() call stack 2021-04-30 11:20:42 -07:00
taskstats.c
test_kprobes.c
torture.c torture: Fix hang during kthread shutdown phase 2023-08-30 16:18:19 +02:00
tracepoint.c tracepoint: Fix kerneldoc comments 2021-08-16 11:39:51 -04:00
tsacct.c taskstats: Cleanup the use of task->exit_code 2022-01-27 11:05:35 +01:00
ucount.c ucounts: Handle wrapping in is_ucounts_overlimit 2022-02-23 12:03:20 +01:00
uid16.c
uid16.h
umh.c kernel/umh.c: fix some spelling mistakes 2021-05-07 00:26:34 -07:00
up.c A set of locking related fixes and updates: 2021-05-09 13:07:03 -07:00
user_namespace.c ucounts: Fix systemd LimitNPROC with private users regression 2022-03-08 19:12:42 +01:00
user-return-notifier.c
user.c fs/epoll: use a per-cpu counter for user's watches count 2021-09-08 11:50:27 -07:00
usermode_driver.c Merge branch 'work.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-07-03 11:41:14 -07:00
utsname_sysctl.c
utsname.c
watch_queue.c kernel: watch_queue: copy user-array safely 2023-11-28 16:56:16 +00:00
watchdog_hld.c watchdog/perf: more properly prevent false positives with turbo modes 2023-07-23 13:46:52 +02:00
watchdog.c watchdog: move softlockup_panic back to early_param 2023-11-28 16:56:28 +00:00
workqueue_internal.h workqueue: Assign a color to barrier work items 2021-08-17 07:49:10 -10:00
workqueue.c Revert "workqueue: remove unused cancel_work()" 2023-12-08 08:48:03 +01:00