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SubjectRe: [V9fs-developer] [PATCH] /net/9p/trans_fd.c: fix race-condition by flushing workqueue before the kfree()
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On 2018/7/20 4:06, Tomas Bortoli wrote:
> The patch adds the flush in p9_mux_poll_stop() as it the function used by
> p9_conn_destroy(), in turn called by p9_fd_close() to stop the async
> polling associated with the data regarding the connection.
>
> Signed-off-by: Tomas Bortoli <tomasbortoli@gmail.com>
> Reported-by: syzbot+39749ed7d9ef6dfb23f6@syzkaller.appspotmail.com
> ---
> As shown by Syzbot, it is possible to provoke a race between p9_fd_close()
> and p9_poll_workfn() that is called to take care of the async read/write work
> to do. To make sure p9_fd_close() frees "trans" when it is not used anymore,
> it has to explicitly call flush_scheduled_work() before the kfree().
>
> net/9p/trans_fd.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
> index bf459ee0feab..76ae134c05d9 100644
> --- a/net/9p/trans_fd.c
> +++ b/net/9p/trans_fd.c
> @@ -185,6 +185,8 @@ static void p9_mux_poll_stop(struct p9_conn *m)
> spin_lock_irqsave(&p9_poll_lock, flags);
> list_del_init(&m->poll_pending_link);
> spin_unlock_irqrestore(&p9_poll_lock, flags);
> +
> + flush_scheduled_work();

I suggest we should use flush_work(&p9_poll_work), flush_scheduled_work is not
suitable.

Thanks.

> }
>
> /**
>

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