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* FAILED: patch "[PATCH] tracing: Undo the registration when enabling the histogram" failed to apply to 6.18-stable tree
@ 2026-09-16 14:18 gregkh
  2026-09-16 18:36 ` [PATCH 6.18.y 1/3] tracing: Remove get_trigger_ops() and add count_func() from trigger ops Sasha Levin
  0 siblings, 1 reply; 6+ messages in thread
From: gregkh @ 2026-09-16 14:18 UTC (permalink / raw)
  To: donggeunyoo.kernel, rostedt, sashiko-bot; +Cc: stable


The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 92383cef66791a0c63a2f27755cadbdb2fbf270b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026091657-justly-crank-ffed@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 92383cef66791a0c63a2f27755cadbdb2fbf270b Mon Sep 17 00:00:00 2001
From: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Date: Mon, 7 Sep 2026 21:44:20 +0900
Subject: [PATCH] tracing: Undo the registration when enabling the histogram
 trigger fails

Commit 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers
list") described how a trigger that is registered but not on file->triggers
ends up freed while still on the global named_triggers list, and moved the
registration down so that hist_trigger_enable() follows it immediately. One
path still gets there. hist_trigger_enable() adds the trigger and takes it
straight back out when the event cannot be enabled:

	list_add_tail_rcu(&data->list, &file->triggers);

	update_cond_flag(file);

	if (trace_event_trigger_enable_disable(file, 1) < 0) {
		list_del_rcu(&data->list);
		update_cond_flag(file);
		ret--;
	}

so the list walk in hist_unregister_trigger() matches nothing, test stays
NULL, and the ->free() that would call del_named_trigger() is skipped.
out_unreg falls through to out_free, which frees the trigger anyway:

 BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0
 Read of size 8 at addr ffff8880091d3160 by task init/1
  find_named_trigger+0xac/0xc0
  hist_register_trigger+0xc1/0xa00
  event_hist_trigger_parse+0x3146/0x6af0
  event_trigger_write+0xce/0x160
 Freed by task 69:
  kfree+0x154/0x420
  trigger_kthread_fn+0xfd/0x160

Leave the trigger where hist_unregister_trigger() can find it and let that
undo the registration, which is the only code that knows all of what
cmd_ops->init() took: the named list entry, the hist_pad reference, the
reference on the trigger a named histogram is shared with, and the copied
cmd_ops. It also pairs the failed trace_event_trigger_enable_disable(),
whose sm_ref and buffered event reference are otherwise left behind.

Since ->free() releases trigger_data and, for a trigger that does not share
its histogram, hist_data with it, out_unreg can no longer fall through to
out_free. For a trigger that does share, hist_register_trigger() has
already destroyed the caller's hist_data, so the fall-through was reading
freed memory there as well.

Move the enable_timestamps check in hist_unregister_trigger() above the
->free() call for the same reason: hist_data does not outlive it once the
trigger being removed is the one that owns it.

Cc: stable@vger.kernel.org
Fixes: 067fe038e70f ("tracing: Add variable reference handling to hist triggers")
Reported-by: Sashiko AI <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/linux-trace-kernel/20260907092944.3950E1F00A3D@smtp.kernel.org/
Link: https://patch.msgid.link/20260907124420.607097-3-donggeunyoo.kernel@gmail.com
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 54c95f9bd0a3..53100287466f 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6670,11 +6670,12 @@ static int hist_trigger_enable(struct event_trigger_data *data,
 
 	update_cond_flag(file);
 
-	if (trace_event_trigger_enable_disable(file, 1) < 0) {
-		list_del_rcu(&data->list);
-		update_cond_flag(file);
+	/*
+	 * On failure the caller undoes the registration, and
+	 * hist_unregister_trigger() can only find the trigger here.
+	 */
+	if (trace_event_trigger_enable_disable(file, 1) < 0)
 		ret--;
-	}
 
 	return ret;
 }
@@ -6752,13 +6753,13 @@ static void hist_unregister_trigger(char *glob,
 		}
 	}
 
-	if (test && test->cmd_ops->free)
-		test->cmd_ops->free(test);
-
 	if (hist_data->enable_timestamps) {
 		if (!hist_data->remove || test)
 			tracing_set_filter_buffering(file->tr, false);
 	}
+
+	if (test && test->cmd_ops->free)
+		test->cmd_ops->free(test);
 }
 
 static bool hist_file_check_refs(struct trace_event_file *file)
@@ -6963,6 +6964,8 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
 	return ret;
  out_unreg:
 	event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
+	/* The unregister frees trigger_data, skip out_free */
+	goto out;
  out_free:
 	remove_hist_vars(hist_data);
 


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* FAILED: patch "[PATCH] tracing: Take the reference before publishing the named" failed to apply to 6.18-stable tree
@ 2026-09-16 14:18 gregkh
  2026-09-16 18:36 ` [PATCH 6.18.y 1/3] tracing: Remove get_trigger_ops() and add count_func() from trigger ops Sasha Levin
  0 siblings, 1 reply; 6+ messages in thread
From: gregkh @ 2026-09-16 14:18 UTC (permalink / raw)
  To: donggeunyoo.kernel, rostedt, sashiko-bot, zanussi; +Cc: stable


The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 0fe23b8eaba0d3372c66b7b31204408da0715edc
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026091636-unreal-encrust-edca@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0fe23b8eaba0d3372c66b7b31204408da0715edc Mon Sep 17 00:00:00 2001
From: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Date: Mon, 7 Sep 2026 21:44:19 +0900
Subject: [PATCH] tracing: Take the reference before publishing the named
 histogram trigger

event_hist_trigger_named_init() puts the trigger on the global
named_triggers list and only then takes the reference on the trigger it
shares its histogram with:

	data->ref++;

	save_named_trigger(data->named_data->name, data);

	ret = event_hist_trigger_init(data->named_data);
	if (ret < 0) {
		kfree(data->cmd_ops);
		data->cmd_ops = &trigger_hist_cmd;
	}

	return ret;

event_hist_trigger_init() fails when alloc_hist_pad() cannot allocate, and
nothing takes the trigger back off the list on the way out.
event_hist_trigger_parse() frees it, and the next lookup by name reads the
freed object:

 BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0
 Read of size 8 at addr ffff888009346860 by task init/1
  find_named_trigger+0xac/0xc0
  hist_register_trigger+0xc1/0xa00
  event_hist_trigger_parse+0x3146/0x6af0
  event_trigger_write+0xce/0x160
 Freed by task 67:
  kfree+0x154/0x420
  trigger_kthread_fn+0xfd/0x160

Do the reference first and publish once it has succeeded, so that nothing
which can fail runs after the trigger becomes findable.

Cc: stable@vger.kernel.org
Fixes: 7ab0fc61ce73 ("tracing: Move histogram trigger variables from stack to per CPU structure")
Reported-by: Sashiko AI <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/linux-trace-kernel/20260907092944.3950E1F00A3D@smtp.kernel.org/
Link: https://patch.msgid.link/20260907124420.607097-2-donggeunyoo.kernel@gmail.com
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Acked-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 1889e310b73c..54c95f9bd0a3 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6371,17 +6371,18 @@ static int event_hist_trigger_named_init(struct event_trigger_data *data)
 {
 	int ret;
 
-	data->ref++;
-
-	save_named_trigger(data->named_data->name, data);
-
 	ret = event_hist_trigger_init(data->named_data);
 	if (ret < 0) {
 		kfree(data->cmd_ops);
 		data->cmd_ops = &trigger_hist_cmd;
+		return ret;
 	}
 
-	return ret;
+	data->ref++;
+
+	save_named_trigger(data->named_data->name, data);
+
+	return 0;
 }
 
 static void event_hist_trigger_named_free(struct event_trigger_data *data)


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* FAILED: patch "[PATCH] tracing: Set the trace clock before registering the histogram" failed to apply to 6.18-stable tree
@ 2026-09-16  8:13 gregkh
  2026-09-16 13:48 ` [PATCH 6.18.y 1/3] tracing: Remove get_trigger_ops() and add count_func() from trigger ops Sasha Levin
  0 siblings, 1 reply; 6+ messages in thread
From: gregkh @ 2026-09-16  8:13 UTC (permalink / raw)
  To: donggeunyoo.kernel, rostedt; +Cc: stable


The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 6ede78d0563a2a3ae3e46f9c07cedb5d79645429
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026091624-amusing-exorcism-4490@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6ede78d0563a2a3ae3e46f9c07cedb5d79645429 Mon Sep 17 00:00:00 2001
From: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Date: Mon, 7 Sep 2026 18:14:15 +0900
Subject: [PATCH] tracing: Set the trace clock before registering the histogram
 trigger

hist_register_trigger() puts the trigger on the global named_triggers
list in cmd_ops->init(), and only then sets the trace clock:

	if (data->cmd_ops->init) {
		ret = data->cmd_ops->init(data);
		if (ret < 0)
			goto out;
	}

	if (hist_data->enable_timestamps) {
		ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
		if (ret) {
			hist_err(tr, HIST_ERR_SET_CLOCK_FAIL, errpos(clock));
			goto out;
		}

The clock string is not checked anywhere before that call, so a named
trigger using common_timestamp with an unknown clock fails after it has
already become findable. event_hist_trigger_parse() then frees it
without taking it off the list, and the next lookup by name reads the
freed object:

 ~# cd /sys/kernel/tracing/events/sched/sched_switch
 ~# echo 'hist:name=foo:keys=common_pid:ts=common_timestamp:clock=bogus' > trigger
 bash: echo: write error: Invalid argument
 ~# echo 'hist:name=foo:keys=common_pid' > trigger

  BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0
  Read of size 8 at addr ffff88800915d760 by task init/1
   find_named_trigger+0xac/0xc0
   hist_register_trigger+0xc1/0x900
   event_hist_trigger_parse+0x3146/0x6af0
   event_trigger_write+0xce/0x160
  Freed by task 63:
   kfree+0x154/0x420
   trigger_kthread_fn+0xfd/0x160

Set the clock before the trigger is registered, so that nothing which
can fail runs after it is published, the way commit 6f86bdeab633
("tracing: Fix bad hist from corrupting named_triggers list") moved the
registration below the rest of the setup.

tracing_set_filter_buffering() is reference counted, so the init failure
path has to drop the reference that the clock block now takes first.

Cc: stable@vger.kernel.org
Fixes: a4072fe85ba3 ("tracing: Add a clock attribute for hist triggers")
Link: https://patch.msgid.link/20260907091415.554535-1-donggeunyoo.kernel@gmail.com
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 5e00da2d5b1a..1889e310b73c 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6631,12 +6631,6 @@ static int hist_register_trigger(char *glob,
 		data->cmd_ops = cmd_ops;
 	}
 
-	if (data->cmd_ops->init) {
-		ret = data->cmd_ops->init(data);
-		if (ret < 0)
-			goto out;
-	}
-
 	if (hist_data->enable_timestamps) {
 		char *clock = hist_data->attrs->clock;
 
@@ -6649,6 +6643,15 @@ static int hist_register_trigger(char *glob,
 		tracing_set_filter_buffering(file->tr, true);
 	}
 
+	if (data->cmd_ops->init) {
+		ret = data->cmd_ops->init(data);
+		if (ret < 0) {
+			if (hist_data->enable_timestamps)
+				tracing_set_filter_buffering(file->tr, false);
+			goto out;
+		}
+	}
+
 	if (named_data) {
 		remove_hist_vars(hist_data);
 		destroy_hist_data(hist_data);


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-09-16 18:36 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-09-16 14:18 FAILED: patch "[PATCH] tracing: Undo the registration when enabling the histogram" failed to apply to 6.18-stable tree gregkh
2026-09-16 18:36 ` [PATCH 6.18.y 1/3] tracing: Remove get_trigger_ops() and add count_func() from trigger ops Sasha Levin
2026-09-16 18:36   ` [PATCH 6.18.y 2/3] tracing: Merge struct event_trigger_ops into struct event_command Sasha Levin
2026-09-16 18:36   ` [PATCH 6.18.y 3/3] tracing: Undo the registration when enabling the histogram trigger fails Sasha Levin
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2026-09-16 14:18 FAILED: patch "[PATCH] tracing: Take the reference before publishing the named" failed to apply to 6.18-stable tree gregkh
2026-09-16 18:36 ` [PATCH 6.18.y 1/3] tracing: Remove get_trigger_ops() and add count_func() from trigger ops Sasha Levin
2026-09-16  8:13 FAILED: patch "[PATCH] tracing: Set the trace clock before registering the histogram" failed to apply to 6.18-stable tree gregkh
2026-09-16 13:48 ` [PATCH 6.18.y 1/3] tracing: Remove get_trigger_ops() and add count_func() from trigger ops Sasha Levin

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