[PATCH 13/38] tomoyo: Implement security hooks for the new mount API [ver #10]

David Howells
2018-07-27T17:32:56Z

Implement the security hook to check the creation of a new mountpoint for
Tomoyo.

As far as I can tell, Tomoyo doesn't make use of the mount data or parse
any mount options, so I haven't implemented any of the fs_context hooks for
it.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
cc: tomoyo-dev-en@lists.sourceforge.jp
cc: linux-security-module@vger.kernel.org
---

security/tomoyo/common.h | 3 +++
security/tomoyo/mount.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
security/tomoyo/tomoyo.c | 15 +++++++++++++++
3 files changed, 63 insertions(+)

diff --git a/security/tomoyo/common.h b/security/tomoyo/common.h
index 539bcdd30bb8..e637ce73f7f9 100644
--- a/security/tomoyo/common.h
+++ b/security/tomoyo/common.h
@@ -971,6 +971,9 @@ int tomoyo_init_request_info(struct tomoyo_request_info *r,
const u8 index);
int tomoyo_mkdev_perm(const u8 operation, const struct path *path,
const unsigned int mode, unsigned int dev);
+int tomoyo_mount_permission_fc(struct fs_context *fc,
+ const struct path *mountpoint,
+ unsigned int mnt_flags);
int tomoyo_mount_permission(const char *dev_name, const struct path *path,
const char *type, unsigned long flags,
void *data_page);
diff --git a/security/tomoyo/mount.c b/security/tomoyo/mount.c
index 7dc7f59b7dde..9ec84ab6f5e1 100644
--- a/security/tomoyo/mount.c
+++ b/security/tomoyo/mount.c
@@ -6,6 +6,7 @@
*/

#include <linux/slab.h>
+#include <linux/fs_context.h>
#include <uapi/linux/mount.h>
#include "common.h"

@@ -236,3 +237,47 @@ int tomoyo_mount_permission(const char *dev_name, const struct path *path,
tomoyo_read_unlock(idx);
return error;
}
+
+/**
+ * tomoyo_mount_permission_fc - Check permission to create a new mount.
+ * @fc: Context describing the object to be mounted.
+ * @mountpoint: The target object to mount on.
+ * @mnt: The MNT_* flags to be set on the mountpoint.
+ *
+ * Check the permission to create a mount of the object described in @fc. Note
+ * that the source object may be a newly created superblock or may be an
+ * existing one picked from the filesystem (bind mount).
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+int tomoyo_mount_permission_fc(struct fs_context *fc,
+ const struct path *mountpoint,
+ unsigned int mnt_flags)
+{
+ struct tomoyo_request_info r;
+ unsigned int ms_flags = 0;
+ int error;
+ int idx;
+
+ if (tomoyo_init_request_info(&r, NULL, TOMOYO_MAC_FILE_MOUNT) ==
+ TOMOYO_CONFIG_DISABLED)
+ return 0;
+
+ /* Convert MNT_* flags to MS_* equivalents. */
+ if (mnt_flags & MNT_NOSUID) ms_flags |= MS_NOSUID;
+ if (mnt_flags & MNT_NODEV) ms_flags |= MS_NODEV;
+ if (mnt_flags & MNT_NOEXEC) ms_flags |= MS_NOEXEC;
+ if (mnt_flags & MNT_NOATIME) ms_flags |= MS_NOATIME;
+ if (mnt_flags & MNT_NODIRATIME) ms_flags |= MS_NODIRATIME;
+ if (mnt_flags & MNT_RELATIME) ms_flags |= MS_RELATIME;
+ if (mnt_flags & MNT_READONLY) ms_flags |= MS_RDONLY;
+
+ idx = tomoyo_read_lock();
+ /* TODO: There may be multiple sources; for the moment, just pick the
+ * first if there is one.
+ */
+ error = tomoyo_mount_acl(&r, fc->source, mountpoint, fc->fs_type->name,
+ ms_flags);
+ tomoyo_read_unlock(idx);
+ return error;
+}
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index e5e349392e7b..c3a0ae4fa7ce 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -391,6 +391,20 @@ static int tomoyo_path_chroot(const struct path *path)
return tomoyo_path_perm(TOMOYO_TYPE_CHROOT, path, NULL);
}

+/**
+ * tomoyo_sb_mount - Target for security_sb_mountpoint().
+ * @fc: Context describing the object to be mounted.
+ * @mountpoint: The target object to mount on.
+ * @mnt_flags: Mountpoint specific options (as MNT_* flags).
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+static int tomoyo_sb_mountpoint(struct fs_context *fc, struct path *mountpoint,
+ unsigned int mnt_flags)
+{
+ return tomoyo_mount_permission_fc(fc, mountpoint, mnt_flags);
+}
+
/**
* tomoyo_sb_mount - Target for security_sb_mount().
*
@@ -521,6 +535,7 @@ static struct security_hook_list tomoyo_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(path_chmod, tomoyo_path_chmod),
LSM_HOOK_INIT(path_chown, tomoyo_path_chown),
LSM_HOOK_INIT(path_chroot, tomoyo_path_chroot),
+ LSM_HOOK_INIT(sb_mountpoint, tomoyo_sb_mountpoint),
LSM_HOOK_INIT(sb_mount, tomoyo_sb_mount),
LSM_HOOK_INIT(sb_umount, tomoyo_sb_umount),
LSM_HOOK_INIT(sb_pivotroot, tomoyo_sb_pivotroot),