linux-kernel - Re: [RESEND][PATCH] ima: Set and clear FMODE_CAN_READ in ima_calc_file

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]

Date:   Wed, 18 Nov 2020 13:28:38 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Silviu Vlasceanu <Silviu.Vlasceanu@...wei.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [RESEND][PATCH] ima: Set and clear FMODE_CAN_READ in
 ima_calc_file_hash()

On Tue, 2020-11-17 at 15:36 -0800, Linus Torvalds wrote:
> Another alternative is to change the policy and say "any write-only
> open gets turned into a read-write open".
> 
> But it needs to be done at *OPEN* time, not randomly afterwards by
> just lying to the 'struct file'.

The ima_file_check hook is at open, but it is immediately after
vfs_open().   Only after the file is opened can we determine if the
file is in policy.  If the file was originally opened without read
permission, a new file instance (dentry_open) with read permission is
opened.  Would limiting opening a new file instance with read
permission to just the ima_file_check hook be acceptable?

thanks,

Mimi