linux-kernel - Re: [PATCH] proc_sysctl: Fix up ->is

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20250613015421.GD1647736@ZenIV>
Date: Fri, 13 Jun 2025 02:54:21 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: NeilBrown <neil@...wn.name>
Cc: Kees Cook <kees@...nel.org>, Joel Granados <joel.granados@...nel.org>,
	linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] proc_sysctl: Fix up ->is_seen() handling

On Fri, Jun 13, 2025 at 10:37:58AM +1000, NeilBrown wrote:
> 
> Some sysctl tables can provide an is_seen() function which reports if
> the sysctl should be visible to the current process.  This is currently
> used to cause d_compare to fail for invisible sysctls.
> 
> This technique might have worked in 2.6.26 when it was implemented, but
> it cannot work now.  In particular if ->d_compare always fails for a
> particular name, then d_alloc_parallel() will always create a new dentry
> and pass it to lookup() resulting in a new inode for every lookup.  I
> tested this by changing sysctl_is_seen() to always return 0.  When
> all sysctls were still visible and repeated lookups (ls -li) reported
> different inode numbers.

What do you mean, "name"?