linux-kernel - Re: [PATCH V1] block: Fix null pointer dereference issue on struct io

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Message-ID: <344bfde9-5f7e-80a2-038f-3bfc387ea678@kernel.org>
Date:   Wed, 17 May 2023 18:31:56 +0900
From:   Damien Le Moal <dlemoal@...nel.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Yu Kuai <yukuai1@...weicloud.com>,
        Pradeep P V K <quic_pragalla@...cinc.com>, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH V1] block: Fix null pointer dereference issue on struct
 io_cq

On 5/17/23 18:21, Christoph Hellwig wrote:
> On Wed, May 17, 2023 at 06:20:19PM +0900, Damien Le Moal wrote:
>> twice for the same icq. The missing rcu lock in ioc_exit_icqs() already was in
>> itself a bug, and the missing flag check is another.
> 
> spinlocks imply a rcu critical section, no need to duplicate it.

Right. And I misread the code. As Yu said, given that ioc_exit_icqs() iterates
the list of icqs under ioc->lock and the ioc is removed from that list under the
same lock, ioc_exit_icqs() should never see an icq that went through
ioc_destroy_icq()...
Very weird.


-- 
Damien Le Moal
Western Digital Research