FAILED: patch "[PATCH] tracing: Correct the refcount if the hist/hist_debug file" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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 <[email protected]>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 0b4ffbe4888a2c71185eaf5c1a02dd3586a9bc04
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025032436-navy-cornfield-5bd2@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 0b4ffbe4888a2c71185eaf5c1a02dd3586a9bc04 Mon Sep 17 00:00:00 2001
From: Tengda Wu <[email protected]>
Date: Fri, 14 Mar 2025 06:53:35 +0000
Subject: [PATCH] tracing: Correct the refcount if the hist/hist_debug file
fails to open

The function event_{hist,hist_debug}_open() maintains the refcount of 'file->tr' and 'file' through tracing_open_file_tr(). However, it does not roll back these counts on subsequent failure paths, resulting in a refcount leak.

A very obvious case is that if the hist/hist_debug file belongs to a specific instance, the refcount leak will prevent the deletion of that instance, as it relies on the condition 'tr->ref == 1' within __remove_instance().

Fix this by calling tracing_release_file_tr() on all failure paths in event_{hist,hist_debug}_open() to correct the refcount.

index ad7419e24055..53dc6719181e 100644
@@ -5689,12 +5689,16 @@ static int event_hist_open(struct inode *inode, struct file *file)
 	guard(mutex)(&event_mutex);
 
 	event_file = event_file_data(file);
-	if (!event_file)
-		return -ENODEV;
+	if (!event_file) {
+		ret = -ENODEV;
+		goto err;
+	}
 
 	hist_file = kzalloc(sizeof(*hist_file), GFP_KERNEL);
-	if (!hist_file)
-		return -ENOMEM;
+	if (!hist_file) {
+		ret = -ENOMEM;
+		goto err;
+	}
 
 	hist_file->file = file;
 	hist_file->last_act = get_hist_hit_count(event_file);

@@ -5702,9 +5706,14 @@ static int event_hist_open(struct inode *inode, struct file *file)
 	/* Clear private_data to avoid warning in single_open() */
 	file->private_data = NULL;
 	ret = single_open(file, hist_show, hist_file);
-	if (ret)
+	if (ret) {
 		kfree(hist_file);
+		goto err;
+	}
 
+	return 0;
+err:
+	tracing_release_file_tr(inode, file);
 	return ret;
 }
 

@@ -5979,7 +5988,10 @@ static int event_hist_debug_open(struct inode *inode, struct file *file)
 
 	/* Clear private_data to avoid warning in single_open() */
 	file->private_data = NULL;
-	return single_open(file, hist_debug_show, file);
+	ret = single_open(file, hist_debug_show, file);
+	if (ret)
+		tracing_release_file_tr(inode, file);
+	return ret;
 }
 
 const struct file_operations event_hist_debug_fops = {