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Date: Thu, 20 Feb 2020 17:39:14 -0600
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Al Viro <viro@...iv.linux.org.uk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linux API <linux-api@...r.kernel.org>, Linux FS Devel <linux-fsdevel@...r.kernel.org>, Linux Security Module <linux-security-module@...r.kernel.org>, Akinobu Mita <akinobu.mita@...il.com>, Alexey Dobriyan <adobriyan@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, "Dmitry V . Levin" <ldv@...linux.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Ingo Molnar <mingo@...nel.org>, "J . Bruce Fields" <bfields@...ldses.org>, Jeff Layton <jlayton@...chiereds.net>, Jonathan Corbet <corbet@....net>, Kees Cook <keescook@...omium.org>, Oleg Nesterov <oleg@...hat.com>, Solar Designer <solar@...nwall.com>
Subject: Re: [PATCH 4/7] proc: Use d_invalidate in proc_prune_siblings_dcache
Al Viro <viro@...iv.linux.org.uk> writes:
> On Thu, Feb 20, 2020 at 10:54:20PM +0000, Al Viro wrote:
>> On Thu, Feb 20, 2020 at 02:49:53PM -0600, Eric W. Biederman wrote:
>> >
>> > The function d_prune_aliases has the problem that it will only prune
>> > aliases thare are completely unused. It will not remove aliases for
>> > the dcache or even think of removing mounts from the dcache. For that
>> > behavior d_invalidate is needed.
>> >
>> > To use d_invalidate replace d_prune_aliases with d_find_alias
>> > followed by d_invalidate and dput. This is safe and complete
>> > because no inode in proc has any hardlinks or aliases.
>>
>> s/no inode.*/it's a fucking directory inode./
>
> Wait... You are using it for sysctls as well? Ho-hum... The thing is,
> for sysctls you are likely to run into consequent entries with the
> same superblock, making for a big pile of useless playing with
> ->s_active... And yes, that applied to mainline as well
Which is why I worked to merge the two cases since they were so close.
Fewer things to fix and more eyeballs on the code.
Eric
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