linux-kernel - [PATCH 2/3] autofs - make dev ioctl version and ismountpoint user accessible

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Date:   Wed, 10 May 2017 12:18:43 +0800
From:   Ian Kent <raven@...maw.net>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Colin Walters <walters@...hat.com>, Ondrej Holy <oholy@...hat.com>,
        autofs mailing list <autofs@...r.kernel.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: [PATCH 2/3] autofs - make dev ioctl version and ismountpoint user
 accessible

Some of the autofs miscellaneous device ioctls need to be accessable to
user space applications without CAP_SYS_ADMIN to get information about
autofs mounts.

Start by making the autofs miscellaneous device ioctl header available
and allow applications to use version and ismountpoint ioctls.

Signed-off-by: Ian Kent <raven@...maw.net>
Cc: Colin Walters <walters@...hat.com>
Cc: Ondrej Holy <oholy@...hat.com>
Cc: stable@...r.kernel.org
---
 fs/autofs4/dev-ioctl.c              |   12 ++++++++----
 include/uapi/linux/Kbuild           |    1 +
 include/uapi/linux/auto_dev-ioctl.h |    2 +-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 9b58d6e..f8cb3f6 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -628,10 +628,6 @@ static int _autofs_dev_ioctl(unsigned int command,
 	ioctl_fn fn = NULL;
 	int err = 0;
 
-	/* only root can play with this */
-	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
 	cmd_first = _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST);
 	cmd = _IOC_NR(command);
 
@@ -640,6 +636,14 @@ static int _autofs_dev_ioctl(unsigned int command,
 		return -ENOTTY;
 	}
 
+	/* Only root can use ioctls other than AUTOFS_DEV_IOCTL_VERSION_CMD
+	 * and AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD
+	 */
+	if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD &&
+	    cmd != AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
 	/* Copy the parameters into kernel space. */
 	param = copy_dev_ioctl(user);
 	if (IS_ERR(param))
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index 662c592..1f22bbb 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -61,6 +61,7 @@ header-y += atm_zatm.h
 header-y += audit.h
 header-y += auto_fs4.h
 header-y += auto_fs.h
+header-y += auto_dev-ioctl.h
 header-y += auxvec.h
 header-y += ax25.h
 header-y += b1lli.h
diff --git a/include/uapi/linux/auto_dev-ioctl.h b/include/uapi/linux/auto_dev-ioctl.h
index 744b3d0..5558db8 100644
--- a/include/uapi/linux/auto_dev-ioctl.h
+++ b/include/uapi/linux/auto_dev-ioctl.h
@@ -16,7 +16,7 @@
 #define AUTOFS_DEVICE_NAME		"autofs"
 
 #define AUTOFS_DEV_IOCTL_VERSION_MAJOR	1
-#define AUTOFS_DEV_IOCTL_VERSION_MINOR	0
+#define AUTOFS_DEV_IOCTL_VERSION_MINOR	1
 
 #define AUTOFS_DEV_IOCTL_SIZE		sizeof(struct autofs_dev_ioctl)