linux-kernel - [PATCH bpf-next v10 01/10] fs,security: Add a new file access type: MAY

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Message-Id: <20190721213116.23476-2-mic@digikod.net>
Date:   Sun, 21 Jul 2019 23:31:07 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     linux-kernel@...r.kernel.org
Cc:     Mickaël Salaün <mic@...ikod.net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Drysdale <drysdale@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        James Morris <jmorris@...ei.org>, Jann Horn <jann@...jh.net>,
        John Johansen <john.johansen@...onical.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Mickaël Salaün <mickael.salaun@....gouv.fr>,
        Paul Moore <paul@...l-moore.com>,
        Sargun Dhillon <sargun@...gun.me>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Shuah Khan <shuah@...nel.org>,
        Stephen Smalley <sds@...ho.nsa.gov>, Tejun Heo <tj@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Thomas Graf <tgraf@...g.ch>, Tycho Andersen <tycho@...ho.ws>,
        Will Drewry <wad@...omium.org>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH bpf-next v10 01/10] fs,security: Add a new file access type: MAY_CHROOT

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@...ikod.net>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Casey Schaufler <casey@...aufler-ca.com>
Cc: James Morris <jmorris@...ei.org>
Cc: John Johansen <john.johansen@...onical.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Paul Moore <paul@...l-moore.com>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Cc: Stephen Smalley <sds@...ho.nsa.gov>
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: linux-fsdevel@...r.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 b5b80469b93d..e8767318fd03 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -494,7 +494,8 @@ int ksys_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 75f2ed289a3f..7a0d92b1da85 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -99,6 +99,7 @@ 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
-- 
2.22.0