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Date: Fri, 6 Sep 2019 17:24:52 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: linux-kernel@...r.kernel.org
Cc: Mickaël Salaün <mic@...ikod.net>,
Aleksa Sarai <cyphar@...har.com>, Alexei Starovoitov <ast@...nel.org>,
Al Viro <viro@...iv.linux.org.uk>, Andy Lutomirski <luto@...nel.org>,
Christian Heimes <christian@...hon.org>,
Daniel Borkmann <daniel@...earbox.net>,
Eric Chiang <ericchiang@...gle.com>,
Florian Weimer <fweimer@...hat.com>, James Morris <jmorris@...ei.org>,
Jan Kara <jack@...e.cz>, Jann Horn <jannh@...gle.com>,
Jonathan Corbet <corbet@....net>, Kees Cook <keescook@...omium.org>,
Matthew Garrett <mjg59@...gle.com>,
Matthew Wilcox <willy@...radead.org>,
Michael Kerrisk <mtk.manpages@...il.com>,
Mickaël Salaün <mickael.salaun@....gouv.fr>,
Mimi Zohar <zohar@...ux.ibm.com>,
Philippe Trébuchet <philippe.trebuchet@....gouv.fr>,
Scott Shell <scottsh@...rosoft.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Shuah Khan <shuah@...nel.org>, Song Liu <songliubraving@...com>,
Steve Dower <steve.dower@...hon.org>, Steve Grubb <sgrubb@...hat.com>,
Thibaut Sautereau <thibaut.sautereau@....gouv.fr>,
Vincent Strubel <vincent.strubel@....gouv.fr>,
Yves-Alexis Perez <yves-alexis.perez@....gouv.fr>,
kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
linux-security-module@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH v2 2/5] fs: Add a MAY_EXECMOUNT flag to infer the noexec mount propertie
An LSM doesn't get path information related to an access request to open
an inode. This new (internal) MAY_EXECMOUNT flag enables an LSM to
check if the underlying mount point of an inode is marked as executable.
This is useful to implement a security policy taking advantage of the
noexec mount option.
This flag is set according to path_noexec(), which checks if a mount
point is mounted with MNT_NOEXEC or if the underlying superblock is
SB_I_NOEXEC.
Signed-off-by: Mickaël Salaün <mic@...ikod.net>
Reviewed-by: Philippe Trébuchet <philippe.trebuchet@....gouv.fr>
Reviewed-by: Thibaut Sautereau <thibaut.sautereau@....gouv.fr>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Kees Cook <keescook@...omium.org>
Cc: Mickaël Salaün <mickael.salaun@....gouv.fr>
---
fs/namei.c | 2 ++
include/linux/fs.h | 2 ++
2 files changed, 4 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c
index 209c51a5226c..0a6b9483d0cb 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2968,6 +2968,8 @@ static int may_open(const struct path *path, int acc_mode, int flag)
break;
}
+ /* Pass the mount point executability. */
+ acc_mode |= path_noexec(path) ? 0 : MAY_EXECMOUNT;
error = inode_permission(inode, MAY_OPEN | acc_mode);
if (error)
return error;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 848f5711bdf0..e57609dac8dd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -101,6 +101,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
#define MAY_NOT_BLOCK 0x00000080
/* the inode is opened with O_MAYEXEC */
#define MAY_OPENEXEC 0x00000100
+/* the mount point is marked as executable */
+#define MAY_EXECMOUNT 0x00000200
/*
* flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond
--
2.23.0
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