From: Neill Kapron <nkapron@google.com>
To: Ingo Rohloff <ingo.rohloff@lauterbach.com>
Cc: gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk,
me@samcday.com, michael.bommarito@gmail.com,
linux-usb@vger.kernel.org
Subject: Re: [PATCH 2/3] usb: gadget: f_fs: register cancellation handler only after request queueing
Date: Fri, 6 Nov 2026 22:47:48 +0000 [thread overview]
Message-ID: <au5ZFAei8LcpYNgY@google.com> (raw)
In-Reply-To: <20260901120908.14386-3-ingo.rohloff@lauterbach.com>
On Tue, Sep 01, 2026 at 02:09:07PM +0200, Ingo Rohloff wrote:
> Call kiocb_set_cancel_fn() only after usb_ep_queue() completes
> successfully.
>
> This also undoes commit e78dcb1f7ec2 ("usb: gadget: f_fs: Fix
> Use-After-Free in AIO error path"): The described error is avoided by
> making sure the cancellation handler is only registered, if there is
> something to cancel.
Hi Ingo,
Unfortunately, I don't think this is safe. The cancel handler has to be
set before the request is queued.
Moving the registration to just before usb_ep_queue() would close the
potential race, but if the queue fails, you still have to unwind- the
kiocb is already on active_reqs, so it has to be removed before io_data
is freed.
That ends up more complex than what we have today, so I'm going to NAK
this patch.
Thanks,
Neill
next prev parent reply other threads:[~2026-11-06 22:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-01 12:09 [PATCH 0/3] usb: gadget: f_fs: cancellation and mm fixes Ingo Rohloff
2026-09-01 12:09 ` [PATCH 1/3] usb: gadget: f_fs: simplify error handling using goto Ingo Rohloff
2026-11-06 23:13 ` Neill Kapron
2026-09-01 12:09 ` [PATCH 2/3] usb: gadget: f_fs: register cancellation handler only after request queueing Ingo Rohloff
2026-11-06 22:47 ` Neill Kapron [this message]
2026-09-01 12:09 ` [PATCH 3/3] usb: gadget: f_fs: Fix mmgrab()/mmdrop() balance Ingo Rohloff
2026-10-30 8:19 ` Hongyu Xie
2026-11-06 22:53 ` Neill Kapron
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