linux-stable.git/kernel/trace, branch v7.2-rc3

ring-buffer: Allow sparse CPU masks in ring_buffer_desc()

2026-07-10T18:04:26+00:00

No user currently relies on sparse CPU masks, but the descriptor logic already
supports them via linear fallback. Remove the arbitrary limitation.

Link: https://patch.msgid.link/20260709160017.1729517-4-vdonnefort@google.com
Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes")
Reported-by: Sashiko 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt

tracing/remotes: Fix struct_len in trace_remote_alloc_buffer()

2026-07-10T18:04:26+00:00

Pre-calculate desc->struct_len up-front in trace_remote_alloc_buffer()
with trace_buffer_desc_size() to fix double-counting.

While at it, use the accessor __first_ring_buffer_desc().

Link: https://patch.msgid.link/20260709160017.1729517-3-vdonnefort@google.com
Fixes: 96e43537af54 ("tracing: Introduce trace remotes")
Reported-by: Sashiko 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt

tracing/remotes: Fix leak in trace_remote_alloc_buffer() error path

2026-07-10T18:04:26+00:00

If page allocation fails in trace_remote_alloc_buffer(), desc->nr_cpus
is not yet incremented for the current CPU. As a consequence, on error,
half-allocated rb_desc will not be freed in trace_remote_free_buffer().

Increment desc->nr_cpus as soon as the first allocation for the current
CPU has succeeded.

Link: https://patch.msgid.link/20260709160017.1729517-2-vdonnefort@google.com
Fixes: 96e43537af54 ("tracing: Introduce trace remotes")
Reported-by: Sashiko 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt

tracing/synthetic: Free type string on error path

2026-07-07T17:59:55+00:00

parse_synth_field() builds a "__data_loc ..." type string before
assigning it to field->type. If the seq_buf check fails, the common
cleanup cannot free the temporary string. Free it before leaving.

Link: https://patch.msgid.link/20260603062533.1096320-2-pengyu@kylinos.cn
Signed-off-by: Yu Peng 
Signed-off-by: Steven Rostedt

tracing/user_events: Fix use-after-free in user_event_mm_dup()

2026-07-07T17:59:35+00:00

user_event_mm_dup() walks the parent mm's enabler list locklessly under
rcu_read_lock() during fork() (from copy_process()); it does not take
event_mutex:

	rcu_read_lock();
	list_for_each_entry_rcu(enabler, &old_mm->enablers, mm_enablers_link)
		enabler->event = user_event_get(orig->event);

user_event_enabler_destroy() removes an enabler from that list with
list_del_rcu() and then, without waiting for a grace period, drops the
enabler's user_event reference with user_event_put() and frees the enabler
with kfree(). A reader that loaded the enabler before the list_del_rcu()
can still be walking it, which leads to two use-after-frees:

 - kfree(enabler) frees the enabler while that reader dereferences
   enabler->event.

 - user_event_put() may drop the last reference to the user_event, which
   is then freed (via delayed_destroy_user_event() on a work queue), while
   the same reader does user_event_get(orig->event) on it.

Both are reachable by an unprivileged task that can open user_events_data:
one multithreaded process that registers an enabler and then concurrently
unregisters it and calls fork() triggers the race. KASAN reports a
slab-use-after-free in user_event_mm_dup() during clone(), with a
"refcount_t: addition on 0" warning when the user_event is freed.

The enabler use-after-free was found first; the user_event one was reported
by XIAO WU, and the earlier enabler-only fix did not address it.

Defer both the user_event_put() and the kfree(enabler) to a work item
queued with queue_rcu_work(), so they run only after an RCU grace period,
once all readers walking the enabler list have finished. The put must run
in process context because user_event_put() takes event_mutex on the last
reference, so a work queue is used rather than call_rcu(). The now-unlocked
put lets the locked argument of user_event_enabler_destroy() be removed;
all callers are updated.

Fixes: 7235759084a4 ("tracing/user_events: Use remote writes for event enablement")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260707165912.2560537-2-michael.bommarito@gmail.com
Reported-by: XIAO WU 
Closes: https://lore.kernel.org/all/tencent_89647CE40DC452B891C65C94D1B271DE8E07@qq.com/
Suggested-by: Beau Belgrave 
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito 
Signed-off-by: Steven Rostedt

tracing: Add a no-rcu-check version of trace_##event##_enabled()

2026-07-07T14:42:29+00:00

Tracepoints require that RCU is watching. To prevent them from being used
in places that RCU is not watching, the trace_##event() macro always
calls rcu_is_watching() even when the event is not enabled and warns if
RCU is not watching. This is to make sure a warning is triggered even if
the tracepoint is never enabled (as it is only a bug when it is).

It was noticed that tracepoints could be hidden within
trace_#event#_enabled() calls, which are used to do extra work for the
tracepoint only if the tracepoint is enabled. But this also can hide the
fact that a tracepoint is placed in a location that can be called when RCU
is not watching.

Commit 9764e731ef6ab ("tracepoint: Add lockdep rcu_is_watching() check to
trace_##name##_enabled()") added a check to the trace_##event##_enabled()
macro to make sure RCU is watching when it is called to make sure not to
hide the bug of a tracepoint being called when RCU is not watching.

There is one case in the irq_disable tracepoint where it is within a
trace_irq_disable_enabled() block, but it checks if RCU is watching, and
if it isn't, it makes a call to ct_irq_enter() that makes RCU watch again.
But because trace_irq_disable_enabled() now checks if RCU is watching and
will trigger if it isn't. This is a false warning as the code within
the block handles this case.

Add a new internal macro __trace_##event##_enabled() that doesn't check if
RCU is watching, and convert the irq_enable/disable tracepoints over to
it.

Link: https://patch.msgid.link/20260701132744.6a7fc68b@robin
Reported-by: Geert Uytterhoeven 
Closes: https://lore.kernel.org/all/CAMuHMdXud_RpWag_hFqa2ByBGRxg6KnxGL1ObCWZrpTsk3TfAw@mail.gmail.com/
Fixes: 9764e731ef6ab ("tracepoint: Add lockdep rcu_is_watching() check to trace_##name##_enabled()")
Tested-by: Geert Uytterhoeven 
Signed-off-by: Steven Rostedt

tracing: Prevent out-of-bounds read in glob matching

2026-07-07T14:42:28+00:00

String event fields are not necessarily NUL-terminated, so the filter
predicate functions (filter_pred_string(), filter_pred_strloc() and
filter_pred_strrelloc()) pass the field length to the regex match
callbacks, and the length-aware matchers honour it.

regex_match_glob() was the exception: it ignored the length and called
glob_match(), which scans the string until it hits a NUL byte. Some
string fields are not NUL-terminated. One example is the dynamic char
array of the xfs_* namespace tracepoints, which is copied without a
trailing NUL. For such a field, glob matching reads past the end of
the event field, causing a KASAN slab-out-of-bounds read in
glob_match(), reached via regex_match_glob() and filter_match_preds()
from the xfs_lookup tracepoint.

Add a length-bounded glob_match_len() and use it from regex_match_glob()
so glob matching always stops at the field boundary. The matching loop
is factored into a shared helper so glob_match() keeps its behaviour.

Fixes: 60f1d5e3bac4 ("ftrace: Support full glob matching")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/da1aaf125fc3b63320b0c540fd6afa7c3d5b4f1a.1782836943.git.hhhuang@smu.edu.sg
Reported-by: Yuan Tan 
Reported-by: Yifan Wu 
Reported-by: Juefei Pu 
Reported-by: Zhengchuan Liang 
Reported-by: Xin Liu 
Assisted-by: Codex:GPT-5.4
Signed-off-by: Huihui Huang 
Signed-off-by: Ren Wei 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt

tracing: Fix NULL pointer dereference in func_set_flag()

2026-07-07T14:42:28+00:00

func_set_flag() dereferences tr->current_trace_flags before verifying
that the current tracer is actually the function tracer. When the active
tracer has been switched away from "function" (e.g., to "wakeup_rt"),
tr->current_trace_flags can be NULL, leading to a NULL pointer
dereference and kernel crash.

The call chain that triggers this is:

  trace_options_write()
    -> __set_tracer_option()
      -> trace->set_flag()          /* func_set_flag */

In func_set_flag(), the first operation is:

  if (!!set == !!(tr->current_trace_flags->val & bit))

This dereferences tr->current_trace_flags unconditionally. The safety
check that guards against a non-function tracer:

  if (tr->current_trace != &function_trace)
      return 0;

is placed *after* the dereference, which is too late.

This was observed with the following crash dump:

  BUG: unable to handle page fault at 0000000000000000
  RIP: func_set_flag+0xd

  Call Trace:
   __set_tracer_option+0x27
   trace_options_write+0x75
   vfs_write+0x12a
   ksys_write+0x66
   do_syscall_64+0x5b

  RIP: ffffffff914c973d  RSP: ff67ec88b01dfdf0  RFLAGS: 00010202
  RAX: 0000000000000000  RBX: ff3a826e80354580  RCX: 0000000000000001
  RDX: 0000000000000001  RSI: 0000000000000000  RDI: ffffffff93918080

The disassembly confirms the fault:

  func_set_flag+0:   mov 0x1f08(%rdi), %rax  ; RAX = tr->current_trace_flags = NULL
  func_set_flag+13:  mov (%rax), %eax        ; page fault: dereference NULL

At the time of the crash:
  tr->current_trace_flags = 0x0 (NULL)
  tr->current_trace = wakeup_rt_tracer (not function_trace)

The scenario is that a process opens a function tracer option file (such
as "func_stack_trace"), then the current tracer is switched to another
tracer (e.g., "wakeup_rt"), which sets current_trace_flags to NULL. When
the process subsequently writes to the option file, func_set_flag() is
invoked and crashes on the NULL dereference.

Fix this by moving the current_trace check before the
current_trace_flags dereference, so that func_set_flag() returns early
when the function tracer is not active.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260624061715.1445655-1-xiangzao@linux.alibaba.com
Fixes: 76680d0d2825 ("tracing: Have function tracer define options per instance")
Signed-off-by: Yuanhe Shu 
Signed-off-by: Steven Rostedt

tracing: Make tracepoint_printk static as not exported

2026-07-07T14:39:12+00:00

The tracepoint_printk symbol is not exported, so make it
static to remove the following sparse warning:

kernel/trace/trace.c:90:5: warning: symbol 'tracepoint_printk' was not declared. Should it be static?

Fixes: dd293df6395a2 ("tracing: Move trace sysctls into trace.c")
Link: https://patch.msgid.link/20260617105822.904164-1-ben.dooks@codethink.co.uk
Signed-off-by: Ben Dooks 
Signed-off-by: Steven Rostedt

ring-buffer: Fix ring_buffer_read_page() copying only one event per page

2026-07-07T14:38:03+00:00

Commit 8928e4a3be34 ("ring-buffer: Show persistent buffer dropped events
in trace_pipe file") split the "commit" variable in
ring_buffer_read_page() into "commit" (raw) and "size" (masked page
size), but the inner copy loop's terminator was changed to compare rpos
against "event_size" instead of "size".

rpos is the cumulative read offset within the page; event_size is the
length of the single event just copied. The loop thus breaks after the
first event, so only one event is copied per call. This regresses the
per-event memcpy path (partial reads, the active commit page, and
mapped/remote buffers) used by splice/trace_pipe_raw and mmap consumers
into a one-event-at-a-time read.

Compare rpos against the page size as the original code did.

Link: https://patch.msgid.link/20260616175538.111628-1-devnexen@gmail.com
Fixes: 8928e4a3be34 ("ring-buffer: Show persistent buffer dropped events in trace_pipe file")
Signed-off-by: David Carlier 
Signed-off-by: Steven Rostedt