From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B09519B3F9; Thu, 25 Jul 2024 17:10:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721927403; cv=none; b=jo+z8rLgcShgIBuilutJOlkDO1vVKt1B14Ikh9SSpMwHci9Qznsb5U/OkJGMFOBNxbLn5nBD4mDIbixLiDOJhwjRLmAMiDLTf1hiSpn7fcMSBafQpA5nFFPZK0j+tCCvRtw7rtbpC80KgEK9t5HTeckdwwmD9sMSqXmkS4Ln9ME= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721927403; c=relaxed/simple; bh=uBdP3W4FKebfPqzkhis1CiagIX57vt/O2fwnyoKKb1M=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=JlWjrz2S6vnXiBEFIwQIRjwYFLDpkfawwZsqCST2EXNA0446jHUMC52aoDb7kHR6a/Uk09Uy5L49I2Xq+0HYlzBL6gFwVPtvoMFta0mnTKN5676e4O5cB4nfGiRCAVA89G+DJbfk7cLQ/93kdTDwYrjCvCuV1dwynpXGqSnsmkY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C0F9C116B1; Thu, 25 Jul 2024 17:10:01 +0000 (UTC) Date: Thu, 25 Jul 2024 13:10:21 -0400 From: Steven Rostedt To: Ajay Kaher Cc: Mathias Krause , Masami Hiramatsu , Ilkka =?UTF-8?B?TmF1bGFww6TDpA==?= , Linus Torvalds , Al Viro , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, regressions@leemhuis.info, Dan Carpenter , Vasavi Sirnapalli , Alexey Makhalov , Florian Fainelli Subject: Re: tracing: user events UAF crash report Message-ID: <20240725131021.788374d0@gandalf.local.home> In-Reply-To: References: <20240719204701.1605950-1-minipli@grsecurity.net> <5083301c-6dc9-45c9-8106-da683ac6bfbb@grsecurity.net> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 25 Jul 2024 22:00:14 +0530 Ajay Kaher wrote: > Thread A (read event) Thread B (remove event) > > . worker_thread() > . delayed_destroy_user_event() > . -> acquire event_mutex > . destroy_user_event() > vfs_read() . > seq_read() . > f_start() -> acquire event_mutex eventfs_remove_dir() > . (waiting) kfree(user) > . (waiting) -> released event_mutex > acquired event_mutex > f_next() > trace_get_fields(): Hmm, I wonder if this would fix it? -- Steve diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index 3a2b46847c8b..e9ed2826ff46 100644 --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -321,6 +321,8 @@ static void user_event_put(struct user_event *user, bool locked) */ refcount_set(&user->refcnt, 1); + user->call.data = NULL; + if (WARN_ON_ONCE(!schedule_work(&user->put_work))) { /* * If we fail we must wait for an admin to attempt delete or @@ -973,6 +975,11 @@ size_t copy_nofault(void *addr, size_t bytes, struct iov_iter *i) static struct list_head *user_event_get_fields(struct trace_event_call *call) { struct user_event *user = (struct user_event *)call->data; + static LIST_HEAD(head); + + /* If the user event is about to be deleted, return no fields */ + if (!user) + return &head; return &user->fields; }