linux-kernel - Re: [PATCH v3 0/7] Add O_DENY* support for VFS and CIFS/NFS

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: <512FD1D5.3010106@mit.edu>
Date:	Thu, 28 Feb 2013 13:53:25 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Pavel Shilovsky <piastry@...rsoft.ru>
CC:	linux-kernel@...r.kernel.org, linux-cifs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	wine-devel@...ehq.org
Subject: Re: [PATCH v3 0/7] Add O_DENY* support for VFS and CIFS/NFS

[possible resend -- sorry]

On 02/28/2013 07:25 AM, Pavel Shilovsky wrote:
> This patchset adds support of O_DENY* flags for Linux fs layer. These flags can be used by any application that needs share reservations to organize a file access. VFS already has some sort of this capability - now it's done through flock/LOCK_MAND mechanis, but that approach is non-atomic. This patchset build new capabilities on top of the existing one but doesn't bring any changes into the flock call semantic.
> 
> These flags can be used by NFS (built-in-kernel) and CIFS (Samba) servers and Wine applications through VFS (for local filesystems) or CIFS/NFS modules. This will help when e.g. Samba and NFS server share the same directory for Windows and Linux users or Wine applications use Samba/NFS share to access the same data from different clients.
> 
> According to the previous discussions the most problematic question is how to prevent situations like DoS attacks where e.g /lib/liba.so file can be open with DENYREAD, or smth like this. That's why one extra flag O_DENYMAND is added. It indicates to underlying layer that an application want to use O_DENY* flags semantic. It allows us not affect native Linux applications (that don't use O_DENYMAND flag) - so, these flags (and the semantic of open syscall that they bring) are used only for those applications that really want it proccessed that way.
> 
> So, we have four new flags:
> O_DENYREAD - to prevent other opens with read access,
> O_DENYWRITE - to prevent other opens with write access,
> O_DENYDELETE - to prevent delete operations (this flag is not implemented in VFS and NFS part and only suitable for CIFS module),
> O_DENYMAND - to switch on/off three flags above.

O_DENYMAND doesn't deny anything.  Would a name like O_RESPECT_DENY be
better?

Other than that, this seems like a sensible mechanism.

--Andy

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/