linux-kernel - Re: [PATCH v2] proc: proc_pid_ns takes super

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Date:   Mon, 18 May 2020 07:57:16 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Alexey Gladkov <gladkov.alexey@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        syzbot <syzbot+c1af344512918c61362c@...kaller.appspotmail.com>,
        jmorris@...ei.org, linux-next@...r.kernel.org,
        linux-security-module@...r.kernel.org, serge@...lyn.com,
        sfr@...b.auug.org.au, syzkaller-bugs@...glegroups.com,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v2] proc: proc_pid_ns takes super_block as an argument

Alexey Gladkov <gladkov.alexey@...il.com> writes:

> On Mon, May 18, 2020 at 07:08:57AM -0500, Eric W. Biederman wrote:
>> Alexey Gladkov <gladkov.alexey@...il.com> writes:
>> 
>> > The proc_pid_ns() can be used for both inode and dentry. To avoid making
>> > two identical functions, change the argument type of the proc_pid_ns().
>> >
>> > Link: https://lore.kernel.org/lkml/c3461e26-1407-2262-c709-dac0df3da2d0@i-love.sakura.ne.jp/
>> > Reported-by: syzbot+c1af344512918c61362c@...kaller.appspotmail.com
>> > Signed-off-by: Alexey Gladkov <gladkov.alexey@...il.com>
>> 
>> So overall this looks good.
>> 
>> However, the description leaves a little bit to be desired as it does
>> not describe why it is bad to use dentry->d_sb.  A fixes tag would be
>> nice if for no other reason than to help anyone who decides to backport
>> this.
>
> OK. I will add it.

Thank you.  It really helps to have the full description of why in
the commit comments.

>> And can you please compile test this?
>> 
>> There is a very silly typo in proc that keeps this from compiling.
>
> I compiled the kernel with this patch and ran the kernel, but accidentally
> did not check children_seq_show(). Sorry.

Yes, children_seq_show is behind a sneaky CONFIG option.

Eric