* [PATCH] perf/ftrace: Fix WARNING in __unregister_ftrace_function
@ 2026-05-13 16:16 Rik van Riel
2026-05-13 16:33 ` Steven Rostedt
0 siblings, 1 reply; 5+ messages in thread
From: Rik van Riel @ 2026-05-13 16:16 UTC (permalink / raw)
To: Steven Rostedt
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel, kernel-team
perf_ftrace_function_unregister() unconditionally calls
unregister_ftrace_function() without checking whether the ftrace_ops
was ever successfully registered. This triggers a WARN_ON in
__unregister_ftrace_function() when the ops doesn't have
FTRACE_OPS_FL_ENABLED set.
This can happen during perf_event_alloc() error cleanup when
perf_trace_destroy() is called via __free_event() on an event whose
ftrace_ops registration failed or was already torn down by
perf_try_init_event()'s err_destroy path.
The call path is:
perf_event_alloc() error cleanup
-> __free_event()
-> event->destroy() [tp_perf_event_destroy]
-> perf_trace_destroy()
-> perf_trace_event_close()
-> TRACE_REG_PERF_CLOSE
-> perf_ftrace_function_unregister()
-> unregister_ftrace_function()
-> __unregister_ftrace_function()
-> WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED))
Fix this by checking FTRACE_OPS_FL_ENABLED before attempting to
unregister. If the ops is not enabled, just free the filter and
return success.
Assisted-by: Claude:claude-opus-4.7 syzkaller
Signed-off-by: Rik van Riel <riel@surriel.com>
---
kernel/trace/trace_event_perf.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index a6bb7577e8c5..b9e33ae24867 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -497,7 +497,14 @@ static int perf_ftrace_function_register(struct perf_event *event)
static int perf_ftrace_function_unregister(struct perf_event *event)
{
struct ftrace_ops *ops = &event->ftrace_ops;
- int ret = unregister_ftrace_function(ops);
+ int ret;
+
+ if (!(ops->flags & FTRACE_OPS_FL_ENABLED)) {
+ ftrace_free_filter(ops);
+ return 0;
+ }
+
+ ret = unregister_ftrace_function(ops);
ftrace_free_filter(ops);
return ret;
}
--
2.53.0-Meta
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] perf/ftrace: Fix WARNING in __unregister_ftrace_function
2026-05-13 16:16 [PATCH] perf/ftrace: Fix WARNING in __unregister_ftrace_function Rik van Riel
@ 2026-05-13 16:33 ` Steven Rostedt
2026-05-13 17:24 ` [PATCH v2] " Rik van Riel
0 siblings, 1 reply; 5+ messages in thread
From: Steven Rostedt @ 2026-05-13 16:33 UTC (permalink / raw)
To: Rik van Riel
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel, kernel-team
On Wed, 13 May 2026 12:16:07 -0400
Rik van Riel <riel@surriel.com> wrote:
> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> index a6bb7577e8c5..b9e33ae24867 100644
> --- a/kernel/trace/trace_event_perf.c
> +++ b/kernel/trace/trace_event_perf.c
> @@ -497,7 +497,14 @@ static int perf_ftrace_function_register(struct perf_event *event)
> static int perf_ftrace_function_unregister(struct perf_event *event)
> {
> struct ftrace_ops *ops = &event->ftrace_ops;
> - int ret = unregister_ftrace_function(ops);
> + int ret;
> +
> + if (!(ops->flags & FTRACE_OPS_FL_ENABLED)) {
> + ftrace_free_filter(ops);
> + return 0;
> + }
> +
> + ret = unregister_ftrace_function(ops);
> ftrace_free_filter(ops);
> return ret;
> }
> --
Instead of duplicating code, what about doing:
static int perf_ftrace_function_unregister(struct perf_event *event)
{
struct ftrace_ops *ops = &event->ftrace_ops;
int ret = 0;
if (ops->flags & FTRACE_OPS_FL_ENABLED)
ret = unregister_ftrace_function(ops);
ftrace_free_filter(ops);
return ret;
}
?
-- Steve
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] perf/ftrace: Fix WARNING in __unregister_ftrace_function
2026-05-13 16:33 ` Steven Rostedt
@ 2026-05-13 17:24 ` Rik van Riel
2026-05-13 18:11 ` Steven Rostedt
0 siblings, 1 reply; 5+ messages in thread
From: Rik van Riel @ 2026-05-13 17:24 UTC (permalink / raw)
To: Steven Rostedt
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel, kernel-team
On Wed, 13 May 2026 12:33:44 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
>
> Instead of duplicating code, what about doing:
That is much nicer. Thank you!
---8<---
From 9de86227b917c49315b7b67aac3a83afae8d792d Mon Sep 17 00:00:00 2001
From: Rik van Riel <riel@meta.com>
Date: Sat, 25 Apr 2026 03:33:54 -0700
Subject: [PATCH] perf/ftrace: Fix WARNING in __unregister_ftrace_function
perf_ftrace_function_unregister() unconditionally calls
unregister_ftrace_function() without checking whether the ftrace_ops
was ever successfully registered. This triggers a WARN_ON in
__unregister_ftrace_function() when the ops doesn't have
FTRACE_OPS_FL_ENABLED set.
This can happen during perf_event_alloc() error cleanup when
perf_trace_destroy() is called via __free_event() on an event whose
ftrace_ops registration failed or was already torn down by
perf_try_init_event()'s err_destroy path.
The call path is:
perf_event_alloc() error cleanup
-> __free_event()
-> event->destroy() [tp_perf_event_destroy]
-> perf_trace_destroy()
-> perf_trace_event_close()
-> TRACE_REG_PERF_CLOSE
-> perf_ftrace_function_unregister()
-> unregister_ftrace_function()
-> __unregister_ftrace_function()
-> WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED))
Fix this by checking FTRACE_OPS_FL_ENABLED before attempting to
unregister. If the ops is not enabled, just free the filter and
return success.
Assisted-by: Claude:claude-opus-4.7 syzkaller
Signed-off-by: Rik van Riel <riel@surriel.com>
---
kernel/trace/trace_event_perf.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index a6bb7577e8c5..58e1b427b576 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -497,7 +497,11 @@ static int perf_ftrace_function_register(struct perf_event *event)
static int perf_ftrace_function_unregister(struct perf_event *event)
{
struct ftrace_ops *ops = &event->ftrace_ops;
- int ret = unregister_ftrace_function(ops);
+ int ret = 0;
+
+ if (ops->flags & FTRACE_OPS_FL_ENABLED)
+ ret = unregister_ftrace_function(ops);
+
ftrace_free_filter(ops);
return ret;
}
--
2.52.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] perf/ftrace: Fix WARNING in __unregister_ftrace_function
2026-05-13 17:24 ` [PATCH v2] " Rik van Riel
@ 2026-05-13 18:11 ` Steven Rostedt
0 siblings, 0 replies; 5+ messages in thread
From: Steven Rostedt @ 2026-05-13 18:11 UTC (permalink / raw)
To: Rik van Riel
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel, kernel-team
On Wed, 13 May 2026 13:24:45 -0400
Rik van Riel <riel@surriel.com> wrote:
> From 9de86227b917c49315b7b67aac3a83afae8d792d Mon Sep 17 00:00:00 2001
> From: Rik van Riel <riel@meta.com>
> Date: Sat, 25 Apr 2026 03:33:54 -0700
> Subject: [PATCH] perf/ftrace: Fix WARNING in __unregister_ftrace_function
>
Can you resend this as a normal patch so that it can be picked up by patchwork.
Otherwise it will be ignored.
Thanks,
-- Steve
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2] perf/ftrace: Fix WARNING in __unregister_ftrace_function
@ 2026-05-13 20:19 Rik van Riel
0 siblings, 0 replies; 5+ messages in thread
From: Rik van Riel @ 2026-05-13 20:19 UTC (permalink / raw)
To: Steven Rostedt
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel, kernel-team
perf_ftrace_function_unregister() unconditionally calls
unregister_ftrace_function() without checking whether the ftrace_ops
was ever successfully registered. This triggers a WARN_ON in
__unregister_ftrace_function() when the ops doesn't have
FTRACE_OPS_FL_ENABLED set.
This can happen during perf_event_alloc() error cleanup when
perf_trace_destroy() is called via __free_event() on an event whose
ftrace_ops registration failed or was already torn down by
perf_try_init_event()'s err_destroy path.
The call path is:
perf_event_alloc() error cleanup
-> __free_event()
-> event->destroy() [tp_perf_event_destroy]
-> perf_trace_destroy()
-> perf_trace_event_close()
-> TRACE_REG_PERF_CLOSE
-> perf_ftrace_function_unregister()
-> unregister_ftrace_function()
-> __unregister_ftrace_function()
-> WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED))
Fix this by checking FTRACE_OPS_FL_ENABLED before attempting to
unregister. If the ops is not enabled, just free the filter and
return success.
Assisted-by: Claude:claude-opus-4.7 syzkaller
Signed-off-by: Rik van Riel <riel@surriel.com>
---
kernel/trace/trace_event_perf.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index a6bb7577e8c5..58e1b427b576 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -497,7 +497,11 @@ static int perf_ftrace_function_register(struct perf_event *event)
static int perf_ftrace_function_unregister(struct perf_event *event)
{
struct ftrace_ops *ops = &event->ftrace_ops;
- int ret = unregister_ftrace_function(ops);
+ int ret = 0;
+
+ if (ops->flags & FTRACE_OPS_FL_ENABLED)
+ ret = unregister_ftrace_function(ops);
+
ftrace_free_filter(ops);
return ret;
}
--
2.52.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
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2026-05-13 16:33 ` Steven Rostedt
2026-05-13 17:24 ` [PATCH v2] " Rik van Riel
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