netdev - Re: [PATCH v10 bpf-next 03/17] bpf: introduce BPF token object

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: <20231127-anvertrauen-geldhahn-08f009fe1af1@brauner>
Date: Mon, 27 Nov 2023 17:05:31 +0100
From: Christian Brauner <brauner@...nel.org>
To: Andrii Nakryiko <andrii@...nel.org>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, paul@...l-moore.com,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, keescook@...omium.org,
	kernel-team@...a.com, sargun@...gun.me
Subject: Re: [PATCH v10 bpf-next 03/17] bpf: introduce BPF token object

> +	if (path.mnt->mnt_root != path.dentry) {

You want to verify that you can only create tokens from the root of the
bpffs mount. So for

  sudo mount -t bpf bpf /mnt

you want bpf tokens to be creatable from:

  fd = open("/mnt")

or from bind-mounts of the fs root:

  sudo mount --bind /mnt /srv
  fd = open("/srv")

but not from

  sudo mount --bind /mnt/foo /opt
  fd = open("/opt")

But I think your current check allows for that because if you bind-mount
/mnt/foo to /opt then fd = open("/opt")

  path.mnt->mnt_root == foo and path.dentry == foo

I think

path.dentry != path.mnt->mnt_sb->s_root

should give you what you want.