linux-kernel - Re: [PATCH] swap_readpage: avoid blk_wake_io

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Message-Id: <20190704123218.87a763f771efad158e1b0a89@linux-foundation.org>
Date:   Thu, 4 Jul 2019 12:32:18 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Qian Cai <cai@....pw>, axboe@...nel.dk, hch@....de,
        peterz@...radead.org, gkohli@...eaurora.org, mingo@...hat.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] swap_readpage: avoid blk_wake_io_task() if !synchronous

On Thu, 4 Jul 2019 18:03:01 +0200 Oleg Nesterov <oleg@...hat.com> wrote:

> swap_readpage() sets waiter = bio->bi_private even if synchronous = F,
> this means that the caller can get the spurious wakeup after return. This
> can be fatal if blk_wake_io_task() does set_current_state(TASK_RUNNING)
> after the caller does set_special_state(), in the worst case the kernel
> can crash in do_task_dead().

I think we need a Fixes: and a cc:stable here?

IIRC, we're fixing 0619317ff8baa2 ("block: add polled wakeup task helper").