Merge patch series "nsfs: validate ioctls"

Christian Brauner <brauner@kernel.org> says:

This series ensures that nsfs protects against ioctl overloading.

* patches from https://lore.kernel.org/r/20250219-work-nsfs-v1-0-21128d73c5e8@kernel.org:
  selftests/nsfs: add ioctl validation tests
  nsfs: validate ioctls

Link: https://lore.kernel.org/r/20250219-work-nsfs-v1-0-21128d73c5e8@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

fs/nsfs.c

@@ -152,19 +152,49 @@ static int copy_ns_info_to_user(const struct mnt_namespace *mnt_ns,
 	return 0;
 }
 
+static bool nsfs_ioctl_valid(unsigned int cmd)
+{
+	switch (cmd) {
+	case NS_GET_USERNS:
+	case NS_GET_PARENT:
+	case NS_GET_NSTYPE:
+	case NS_GET_OWNER_UID:
+	case NS_GET_MNTNS_ID:
+	case NS_GET_PID_FROM_PIDNS:
+	case NS_GET_TGID_FROM_PIDNS:
+	case NS_GET_PID_IN_PIDNS:
+	case NS_GET_TGID_IN_PIDNS:
+		return (_IOC_TYPE(cmd) == _IOC_TYPE(cmd));
+	}
+
+	/* Extensible ioctls require some extra handling. */
+	switch (_IOC_NR(cmd)) {
+	case _IOC_NR(NS_MNT_GET_INFO):
+	case _IOC_NR(NS_MNT_GET_NEXT):
+	case _IOC_NR(NS_MNT_GET_PREV):
+		return (_IOC_TYPE(cmd) == _IOC_TYPE(cmd));
+	}
+
+	return false;
+}
+
 static long ns_ioctl(struct file *filp, unsigned int ioctl,
 			unsigned long arg)
 {
 	struct user_namespace *user_ns;
 	struct pid_namespace *pid_ns;
 	struct task_struct *tsk;
-	struct ns_common *ns = get_proc_ns(file_inode(filp));
+	struct ns_common *ns;
 	struct mnt_namespace *mnt_ns;
 	bool previous = false;
 	uid_t __user *argp;
 	uid_t uid;
 	int ret;
 
+	if (!nsfs_ioctl_valid(ioctl))
+		return -ENOIOCTLCMD;
+
+	ns = get_proc_ns(file_inode(filp));
 	switch (ioctl) {
 	case NS_GET_USERNS:
 		return open_related_ns(ns, ns_get_owner);

tools/testing/selftests/filesystems/nsfs/iterate_mntns.c

@@ -3,6 +3,8 @@
 
 #define _GNU_SOURCE
 #include <fcntl.h>
+#include <linux/auto_dev-ioctl.h>
+#include <linux/errno.h>
 #include <sched.h>
 #include <stdio.h>
 #include <string.h>
@@ -146,4 +148,16 @@ TEST_F(iterate_mount_namespaces, iterate_backward)
 	}
 }
 
+TEST_F(iterate_mount_namespaces, nfs_valid_ioctl)
+{
+	ASSERT_NE(ioctl(self->fd_mnt_ns[0], AUTOFS_DEV_IOCTL_OPENMOUNT, NULL), 0);
+	ASSERT_EQ(errno, ENOTTY);
+
+	ASSERT_NE(ioctl(self->fd_mnt_ns[0], AUTOFS_DEV_IOCTL_CLOSEMOUNT, NULL), 0);
+	ASSERT_EQ(errno, ENOTTY);
+
+	ASSERT_NE(ioctl(self->fd_mnt_ns[0], AUTOFS_DEV_IOCTL_READY, NULL), 0);
+	ASSERT_EQ(errno, ENOTTY);
+}
+
 TEST_HARNESS_MAIN