From: Vincent Donnefort <vdonnefort@google.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Qing Wang <wangqing7171@gmail.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
syzbot+3b5dd2030fe08afdf65d@syzkaller.appspotmail.com
Subject: Re: [PATCH] tracing: Fix WARN_ON in tracing_buffers_mmap_close
Date: Fri, 27 Feb 2026 15:16:50 +0000 [thread overview]
Message-ID: <aaG1Yl-HbPG3Buil@google.com> (raw)
In-Reply-To: <20260227101002.614add75@gandalf.local.home>
On Fri, Feb 27, 2026 at 10:10:02AM -0500, Steven Rostedt wrote:
> On Fri, 27 Feb 2026 10:41:17 +0000
> Vincent Donnefort <vdonnefort@google.com> wrote:
>
> > > Hum, not sure this is entirely correct. We do set VM_DONTCOPY when creating the
> > > mapping (see __rb_map_vma). So AFAICT ->open() is not called in this situation (see
> > > dup_mmap())
> >
> > Ah right, Syzkaller is using madvise(MADVISE_DOFORK) which resets VM_DONTCOPY.
>
> Hmm,
>
> So this means user space can override the DONTCOPY? Can this cause bugs
> elsewhere that DONTCOPY is used?
Indeed, user space can clear DONTCOPY... unless we also set VM_IO.
>
> -- Steve
prev parent reply other threads:[~2026-02-27 15:16 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 2:58 [PATCH] tracing: Fix WARN_ON in tracing_buffers_mmap_close Qing Wang
2026-02-27 10:02 ` Vincent Donnefort
2026-02-27 10:41 ` Vincent Donnefort
2026-02-27 11:22 ` Vincent Donnefort
2026-02-27 15:20 ` Steven Rostedt
2026-02-27 20:56 ` Steven Rostedt
2026-03-02 12:13 ` Lorenzo Stoakes
2026-03-02 16:52 ` Steven Rostedt
2026-03-03 10:19 ` Lorenzo Stoakes
2026-03-03 15:25 ` Steven Rostedt
2026-03-04 17:30 ` Lorenzo Stoakes (Oracle)
2026-02-28 8:59 ` Qing Wang
2026-02-27 15:10 ` Steven Rostedt
2026-02-27 15:16 ` Vincent Donnefort [this message]
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