linux-kernel - Re: [PATCH ghak21 V4 1/2] audit: remove path param from link denied function

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Date:   Mon, 16 Apr 2018 10:55:13 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Eric Paris <eparis@...hat.com>,
        Paul Moore <paul@...l-moore.com>,
        Steve Grubb <sgrubb@...hat.com>
Subject: Re: [PATCH ghak21 V4 1/2] audit: remove path param from link denied function

On Wed, Mar 21, 2018 at 1:42 AM, Richard Guy Briggs <rgb@...hat.com> wrote:
> In commit 45b578fe4c3cade6f4ca1fc934ce199afd857edc
> ("audit: link denied should not directly generate PATH record")
> the need for the struct path *link parameter was removed.
> Remove the now useless struct path argument.
>
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
>  fs/namei.c            | 4 ++--
>  include/linux/audit.h | 6 ++----
>  kernel/audit.c        | 3 +--
>  3 files changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 9cc91fb..e3682bb 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -945,7 +945,7 @@ static inline int may_follow_link(struct nameidata *nd)
>         if (nd->flags & LOOKUP_RCU)
>                 return -ECHILD;
>
> -       audit_log_link_denied("follow_link", &nd->stack[0].link);
> +       audit_log_link_denied("follow_link");
>         return -EACCES;
>  }
>
> @@ -1011,7 +1011,7 @@ static int may_linkat(struct path *link)
>         if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
>                 return 0;
>
> -       audit_log_link_denied("linkat", link);
> +       audit_log_link_denied("linkat");
>         return -EPERM;
>  }

This removed the "link" details in both cases, and then commit
ea841bafda3f ("audit: add refused symlink to audit_names") added back
one of them:

> diff --git a/fs/namei.c b/fs/namei.c
> index e3682bb72cb5..5f8e8e2732e1 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -945,6 +945,7 @@ static inline int may_follow_link(struct nameidata *nd)
>         if (nd->flags & LOOKUP_RCU)
>                 return -ECHILD;
>
> +       audit_inode(nd->name, nd->stack[0].link.dentry, 0);
>         audit_log_link_denied("follow_link");
>         return -EACCES;
>  }

Why remove it in the first place, and why add it back open-coded in
only one place?

-Kees

-- 
Kees Cook
Pixel Security