From: Kirill Tkhai <ktkhai@virtuozzo.com>
To: Jens Axboe <axboe@kernel.dk>, LKML <linux-kernel@vger.kernel.org>,
io-uring@vger.kernel.org
Subject: io_uring: io_grab_files() misses taking files->count?
Date: Thu, 6 Feb 2020 19:32:20 +0300 [thread overview]
Message-ID: <f0d2b7d3-2f6b-7eb2-aee0-4ff6a7daa35c@virtuozzo.com> (raw)
Hi, Jens,
in io_grab_files() we take pointer to current->files without taking files->count.
Later, this files become attached to worker in io_worker_handle_work() also without
any manipulation with counter.
But files->count is used for different optimizations. Say, in expand_fdtable() we
avoid synchonize_rcu() in case of there is only files user. In case of there are
more users, missing of synchronize_rcu() is not safe.
Is this correct? Or maybe there is some hidden logic in io_uring, which prevents
this problem? Say, IORING_OP_OPENAT/CLOSE/ETC can't be propagated to worker etc...
Kirill
next reply other threads:[~2020-02-06 16:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-06 16:32 Kirill Tkhai [this message]
2020-02-06 19:55 ` io_uring: io_grab_files() misses taking files->count? Jens Axboe
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