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Date: Wed, 12 Dec 2018 09:17:09 +0100
From: Mickaël Salaün <>
Cc: Mickaël Salaün <>,
        Al Viro <>, James Morris <>,
        Jonathan Corbet <>, Kees Cook <>,
        Matthew Garrett <>,
        Michael Kerrisk <>,
        Mickaël Salaün <>,
        Mimi Zohar <>,
        Philippe Trébuchet <>,
        Shuah Khan <>,
        Thibaut Sautereau <>,
        Vincent Strubel <>,
        Yves-Alexis Perez <>,,,,
Subject: [RFC PATCH v1 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

Signed-off-by: Mickaël Salaün <>
Reviewed-by: Philippe Trébuchet <>
Reviewed-by: Thibaut Sautereau <>
Cc: Al Viro <>
Cc: Kees Cook <>
Cc: Mickaël Salaün <>
 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 0cab6494978c..de4f33b3f464 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2970,6 +2970,8 @@ static int may_open(const struct path *path, int acc_mode, int flag)
+	/* 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 584c9329ad78..083a31b8068e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -96,6 +96,8 @@ 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

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