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Message-ID: <8404022493c5ceda74807a3407e5a087425678e2.camel@redhat.com>
Date: Thu, 26 Oct 2023 10:49:18 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Sascha Hauer <s.hauer@...gutronix.de>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Jens Axboe <axboe@...nel.dk>,
kernel@...gutronix.de
Subject: Re: [PATCH] net: Do not break out of sk_stream_wait_memory() with
TIF_NOTIFY_SIGNAL
On Thu, 2023-10-26 at 09:03 +0200, Sascha Hauer wrote:
> On Tue, Oct 24, 2023 at 03:56:17PM +0200, Paolo Abeni wrote:
> > On Mon, 2023-10-23 at 14:13 +0200, Sascha Hauer wrote:
> > > It can happen that a socket sends the remaining data at close() time.
> > > With io_uring and KTLS it can happen that sk_stream_wait_memory() bails
> > > out with -512 (-ERESTARTSYS) because TIF_NOTIFY_SIGNAL is set for the
> > > current task. This flag has been set in io_req_normal_work_add() by
> > > calling task_work_add().
> > >
> > > It seems signal_pending() is too broad, so this patch replaces it with
> > > task_sigpending(), thus ignoring the TIF_NOTIFY_SIGNAL flag.
> >
> > This looks dangerous, at best. Other possible legit users setting
> > TIF_NOTIFY_SIGNAL will be broken.
> >
> > Can't you instead clear TIF_NOTIFY_SIGNAL in io_run_task_work() ?
>
> I don't have an idea how io_run_task_work() comes into play here, but it
> seems it already clears TIF_NOTIFY_SIGNAL:
>
> static inline int io_run_task_work(void)
> {
> /*
> * Always check-and-clear the task_work notification signal. With how
> * signaling works for task_work, we can find it set with nothing to
> * run. We need to clear it for that case, like get_signal() does.
> */
> if (test_thread_flag(TIF_NOTIFY_SIGNAL))
> clear_notify_signal();
> ...
> }
I see, io_run_task_work() is too late, sk_stream_wait_memory() is
already woken up.
I still think this patch is unsafe. What about explicitly handling the
restart in tls_sw_release_resources_tx() ? The main point is that such
function is called by inet_release() and the latter can't be re-
started.
Cheers,
Paolo
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