linux-kernel - Re: [PATCH -next 2/6] md: remove flag RemoveSynchronized

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAPhsuW4+bn41+LK1y_RmssmwpMML15=WVo6iTL76x8CATzKE3A@mail.gmail.com>
Date:   Wed, 18 Oct 2023 10:53:59 -0700
From:   Song Liu <song@...nel.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next 2/6] md: remove flag RemoveSynchronized

On Sun, Oct 15, 2023 at 6:28 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> rcu is not used correctly here, because synchronize_rcu() is called
> before replacing old value, for example:
>
> remove_and_add_spares   // other path
>  synchronize_rcu
>  // called before replacing old value
>  set_bit(RemoveSynchronized)
>                         rcu_read_lock()
>                         rdev = conf->mirros[].rdev
>  pers->hot_remove_disk
>   conf->mirros[].rdev = NULL;
>   if (!test_bit(RemoveSynchronized))
>    synchronize_rcu
>    /*
>     * won't be called, and won't wait
>     * for concurrent readers to be done.
>     /*
>                         // access rdev after remove_and_add_spares()
>                         rcu_read_unlock()

I am having a hard time following the description here. Please be more
specific about what issue we are fixing here.

Thanks,
Song

>
> Hence remove this flag and prepare to remove rcu protection to access
> rdev from 'conf'.
>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
[...]