linux-kernel - Re: [PATCH] blk_init_allocated_queue() set q->fq as NULL in the fail case

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Date:   Mon, 30 Jul 2018 05:11:58 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "jin.xiao@...el.com" <jin.xiao@...el.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "yanmin.zhang@...el.com" <yanmin.zhang@...el.com>
Subject: Re: [PATCH] blk_init_allocated_queue() set q->fq as NULL in the fail
 case

On Mon, 2018-07-30 at 10:03 +0800, xiao jin wrote:
> We find the memory use-after-free issue in __blk_drain_queue()
> on the kernel 4.14. After read the latest kernel 4.18-rc6 we
> think it has the same problem.
> 
> Memory is allocated for q->fq in the blk_init_allocated_queue().
> If the elevator init function called with error return, it will
> run into the fail case to free the q->fq.
> 
> Then the __blk_drain_queue() uses the same memory after the free
> of the q->fq, it will lead to the unpredictable event.
> 
> The patch is to set q->fq as NULL in the fail case of
> blk_init_allocated_queue().

Please add "Fixes:" and "Cc: stable" tags to this patch.

Thanks,

Bart.