linux-kernel - Re: [PATCH v2 5/5] uprobes: make uprobe

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Message-ID: <20240801120018.GB4038@redhat.com>
Date: Thu, 1 Aug 2024 14:00:18 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>, andrii@...nel.org,
	mhiramat@...nel.org, peterz@...radead.org, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] uprobes: make uprobe_register() return struct
 uprobe *

On 08/01, Jiri Olsa wrote:
>
> > @@ -474,10 +477,10 @@ static void testmod_unregister_uprobe(void)
> >  {
> >         mutex_lock(&testmod_uprobe_mutex);
> >
> > -       if (uprobe.offset) {
> > -               uprobe_unregister(d_real_inode(uprobe.path.dentry),
> > -                                 uprobe.offset, &uprobe.consumer);
> > +       if (uprobe.uprobe) {
> > +               uprobe_unregister(uprobe.uprobe, &uprobe.consumer);
> >                 uprobe.offset = 0;
> > +               uprobe.uprobe = NULL;
>
> ugh, I think we leak &uprobe.path.. I can send follow up fix if needed

Yeah, with or without this change. And with this change we do not need uprobe.offset.

Please see the patch below, this is what I've added to 5/5.

Do you see any problems?

Note the additional path_put() in testmod_unregister_uprobe(). Does it need
a separate patch or can it come with 5/5 ?

Oleg.

--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -432,7 +432,7 @@ uprobe_ret_handler(struct uprobe_consumer *self, unsigned long func,
 
 struct testmod_uprobe {
 	struct path path;
-	loff_t offset;
+	struct uprobe *uprobe;
 	struct uprobe_consumer consumer;
 };
 
@@ -446,25 +446,25 @@ static int testmod_register_uprobe(loff_t offset)
 {
 	int err = -EBUSY;
 
-	if (uprobe.offset)
+	if (uprobe.uprobe)
 		return -EBUSY;
 
 	mutex_lock(&testmod_uprobe_mutex);
 
-	if (uprobe.offset)
+	if (uprobe.uprobe)
 		goto out;
 
 	err = kern_path("/proc/self/exe", LOOKUP_FOLLOW, &uprobe.path);
 	if (err)
 		goto out;
 
-	err = uprobe_register(d_real_inode(uprobe.path.dentry),
-			      offset, 0, &uprobe.consumer);
-	if (err)
+	uprobe.uprobe = uprobe_register(d_real_inode(uprobe.path.dentry),
+					offset, 0, &uprobe.consumer);
+	if (IS_ERR(uprobe.uprobe)) {
+		err = PTR_ERR(uprobe.uprobe);
 		path_put(&uprobe.path);
-	else
-		uprobe.offset = offset;
-
+		uprobe.uprobe = NULL;
+	}
 out:
 	mutex_unlock(&testmod_uprobe_mutex);
 	return err;
@@ -474,10 +474,10 @@ static void testmod_unregister_uprobe(void)
 {
 	mutex_lock(&testmod_uprobe_mutex);
 
-	if (uprobe.offset) {
-		uprobe_unregister(d_real_inode(uprobe.path.dentry),
-				  uprobe.offset, &uprobe.consumer);
-		uprobe.offset = 0;
+	if (uprobe.uprobe) {
+		uprobe_unregister(uprobe.uprobe, &uprobe.consumer);
+		path_put(&uprobe.path);
+		uprobe.uprobe = NULL;
 	}
 
 	mutex_unlock(&testmod_uprobe_mutex);