linux-kernel - Re: [PATCH 3/3] uprobes: make uprobe

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Message-ID: <CAEf4Bzb0ErnW0o09fk2TCJnY3LNW7U4aB0YcUJqKjfNH+m-uyA@mail.gmail.com>
Date: Thu, 11 Jul 2024 10:11:58 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: andrii@...nel.org, mhiramat@...nel.org, peterz@...radead.org, clm@...a.com, 
	jolsa@...nel.org, mingo@...nel.org, paulmck@...nel.org, rostedt@...dmis.org, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] uprobes: make uprobe_register() return struct uprobe *

On Thu, Jul 11, 2024 at 2:28 AM Oleg Nesterov <oleg@...hat.com> wrote:
>
> On 07/10, Oleg Nesterov wrote:
> >
> > -void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> > +void uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
> >  {
> > -     struct uprobe *uprobe;
> > -
> > -     uprobe = find_uprobe(inode, offset);
> > -     if (WARN_ON(!uprobe))
> > -             return;
> > -
> >       down_write(&uprobe->register_rwsem);
> >       __uprobe_unregister(uprobe, uc);
> >       up_write(&uprobe->register_rwsem);
> > -     put_uprobe(uprobe);
>
> OK, this is obviously wrong, needs get_uprobe/put_uprobe. __uprobe_unregister()
> can free this uprobe, so up_write(&uprobe->register_rwsem) is not safe.

uprobe_register(), given it returns an uprobe instance to the caller
should keep refcount on it (it belongs to uprobe_consumer). That's
what I did for my patches, are you going to do that as well?

We basically do the same thing, just interfaces look a bit different.


>
> I'll send V2 on top of Peter's new version.
>
> Oleg.
>