From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>
Subject: [PATCH bpf-next v8 02/11] fs,security: Add a new file access type: MAY_CHROOT
Date: Tue, 27 Feb 2018 01:41:12 +0100
Message-ID: <20180227004121.3633-3-mic@digikod.net>
References: <20180227004121.3633-1-mic@digikod.net>
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To: linux-kernel@vger.kernel.org
Cc: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>, Alexei Starovoitov <ast@kernel.org>, Andy Lutomirski <luto@amacapital.net>, Arnaldo Carvalho de Melo <acme@kernel.org>, Casey Schaufler <casey@schaufler-ca.com>, Daniel Borkmann <daniel@iogearbox.net>, David Drysdale <drysdale@google.com>, "David S . Miller" <davem@davemloft.net>, "Eric W . Biederman" <ebiederm@xmission.com>, James Morris <james.l.morris@oracle.com>, Jann Horn <jann@thejh.net>, Jonathan Corbet <corbet@lwn.net>, Michael Kerrisk <mtk.manpages@gmail.com>, Kees Cook <keescook@chromium.org>, Paul Moore <paul@paul-moore.com>, Sargun Dhillon <sargun@sargun.me>, "Serge E . Hallyn" <serge@hallyn.com>, Shuah Khan <shuah@kernel.org>, Tejun Heo <tj@kernel.org>, Thomas Graf <tgraf@suug.ch>, Tycho
List-Id: linux-api@vger.kernel.org

For compatibility reason, MAY_CHROOT is always set with MAY_CHDIR.
However, this new flag enable to differentiate a chdir form a chroot.

This is needed for the Landlock LSM to be able to evaluate a new root
directory.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: James Morris <jmorris@namei.org>
Cc: John Johansen <john.johansen@canonical.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: linux-fsdevel@vger.kernel.org
---
 fs/open.c          | 3 ++-
 include/linux/fs.h | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/open.c b/fs/open.c
index 7ea118471dce..084d147c0e96 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -489,7 +489,8 @@ SYSCALL_DEFINE1(chroot, const char __user *, filename)
 	if (error)
 		goto out;
 
-	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
+	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR |
+			MAY_CHROOT);
 	if (error)
 		goto dput_and_out;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2a815560fda0..67c62374446c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -90,6 +90,7 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
 #define MAY_CHDIR		0x00000040
 /* called from RCU mode, don't block */
 #define MAY_NOT_BLOCK		0x00000080
+#define MAY_CHROOT		0x00000100
 
 /*
  * flags in file.f_mode.  Note that FMODE_READ and FMODE_WRITE must correspond
-- 
2.16.2