Support setns via nsfs

kernel/src/device/evdev/file.rs

@@ -502,6 +502,10 @@ impl FileIo for EvdevFile {
 
         Ok(0)
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }
 
 impl Drop for EvdevFile {

kernel/src/device/fb.rs

@@ -517,6 +517,10 @@ impl FileIo for FbHandle {
             }
         })
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }
 
 pub(super) fn init_in_first_kthread() {

kernel/src/device/mem/file.rs

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 
 use alloc::vec;
+use core::any::Any;
 
 use ostd::mm::{FallibleVmWrite, VmReader, VmWriter};
 
@@ -150,4 +151,8 @@ impl FileIo for MemFile {
     fn is_offset_aware(&self) -> bool {
         false
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }

kernel/src/device/misc/tdxguest.rs

@@ -170,6 +170,10 @@ impl FileIo for TdxGuestFile {
             _ => return_errno_with_message!(Errno::ENOTTY, "the ioctl command is unknown"),
         })
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }
 
 pub fn tdx_get_quote(inblob: &[u8]) -> Result<Box<[u8]>> {

kernel/src/device/pty/file.rs

@@ -91,4 +91,8 @@ impl FileIo for PtySlaveFile {
     fn is_offset_aware(&self) -> bool {
         false
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }

kernel/src/device/pty/master.rs

@@ -252,6 +252,10 @@ impl FileIo for PtyMaster {
 
         Ok(0)
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }
 
 impl Drop for PtyMaster {

kernel/src/device/registry/block.rs

@@ -151,6 +151,10 @@ impl FileIo for OpenBlockFile {
             ),
         })
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }
 
 pub(super) fn lookup(id: DeviceId) -> Option<Arc<dyn Device>> {

kernel/src/device/tty/n_tty.rs

@@ -185,6 +185,10 @@ impl<D: TtyDriver> FileIo for TtyFile<D> {
     fn is_offset_aware(&self) -> bool {
         false
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }
 
 static TTY1: Once<Arc<Tty<VtDriver>>> = Once::new();

kernel/src/fs/inode_handle.rs

@@ -14,6 +14,7 @@ use crate::{
         file_table::FdFlags,
         path::Path,
         pipe::PipeHandle,
+        pseudofs::{NsCommonOps, NsFile},
         utils::{
             AccessMode, AtomicStatusFlags, CreationFlags, DirentVisitor, FallocMode, FileRange,
             FlockItem, InodeType, OFFSET_MAX, RangeLockItem, RangeLockType, SeekFrom, StatusFlags,
@@ -215,6 +216,11 @@ impl InodeHandle {
 
         Ok(())
     }
+
+    pub fn as_ns_file<T: NsCommonOps>(&self) -> Option<&NsFile<T>> {
+        let file_io = self.file_io.as_ref()?;
+        file_io.as_any().downcast_ref::<NsFile<T>>()
+    }
 }
 
 impl Pollable for InodeHandle {
@@ -519,6 +525,8 @@ pub trait FileIo: Pollable + InodeIo + Any + Send + Sync + 'static {
     fn ioctl(&self, _raw_ioctl: RawIoctl) -> Result<i32> {
         return_errno_with_message!(Errno::ENOTTY, "ioctl is not supported");
     }
+
+    fn as_any(&self) -> &dyn Any;
 }
 
 fn do_seek_util(offset: &Mutex<usize>, pos: SeekFrom, end: Option<usize>) -> Result<usize> {

kernel/src/fs/pipe/common.rs

@@ -136,6 +136,10 @@ impl FileIo for PipeHandle {
     fn is_offset_aware(&self) -> bool {
         false
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
 }
 
 /// A pipe (FIFO) that provides inter-process communication.

kernel/src/syscall/setns.rs

@@ -11,7 +11,10 @@
 //! 2. A `PidFile` opened by `pidfd_open` or by opening `/proc/[pid]` directory.
 
 use crate::{
-    fs::{file_table::FileDesc, path::MountNamespace},
+    fs::{
+        file_handle::FileLike, file_table::FileDesc, inode_handle::InodeHandle,
+        path::MountNamespace, pseudofs::NsCommonOps,
+    },
     net::uts_ns::UtsNamespace,
     prelude::*,
     process::{
@@ -34,13 +37,8 @@ pub fn sys_setns(fd: FileDesc, flags: u32, ctx: &Context) -> Result<SyscallRetur
 
     let new_ns_proxy = if let Some(pid_file) = file.downcast_ref::<PidFile>() {
         build_proxy_from_pid_file(pid_file, ns_type_flags, ctx)?
-    }
+    } else {
-    // TODO: Support setting namespaces from `/proc/[pid]/ns`.
+        build_proxy_from_ns_file(file.as_ref(), ns_type_flags, ctx)?
-    else {
-        return_errno_with_message!(
-            Errno::EINVAL,
-            "the FD does not refer to a supported namespace file"
-        );
     };
 
     // Install the newly created `NsProxy`.
@@ -105,6 +103,56 @@ fn build_proxy_from_pid_file(
     Ok(builder.build())
 }
 
+fn build_proxy_from_ns_file(
+    file: &dyn FileLike,
+    flags: CloneFlags,
+    ctx: &Context,
+) -> Result<NsProxy> {
+    check_unsupported_ns_flags(flags)?;
+
+    let inode_handle = file
+        .downcast_ref::<InodeHandle>()
+        .ok_or_else(|| Error::with_message(Errno::EINVAL, "the file is not a ns file"))?;
+
+    let current_proxy = ctx.thread_local.borrow_ns_proxy();
+    let current_proxy = current_proxy.unwrap();
+
+    let mut builder = NsProxyBuilder::new(current_proxy);
+
+    let applied = try_apply_ns::<UtsNamespace>(inode_handle, flags, |ns| {
+        builder.uts_ns(ns);
+    })? || try_apply_ns::<MountNamespace>(inode_handle, flags, |ns| {
+        builder.mnt_ns(ns);
+    })?;
+    // TODO: Support setting other namespaces from the ns file.
+
+    if !applied {
+        return_errno_with_message!(Errno::EINVAL, "invalid flags are specified with a ns file");
+    }
+
+    Ok(builder.build())
+}
+
+fn try_apply_ns<T: NsCommonOps>(
+    inode_handle: &InodeHandle,
+    flags: CloneFlags,
+    apply: impl FnOnce(Arc<T>),
+) -> Result<bool> {
+    let Some(ns_file) = inode_handle.as_ns_file::<T>() else {
+        return Ok(false);
+    };
+
+    if !flags.is_empty() && flags != T::TYPE.into() {
+        return_errno_with_message!(
+            Errno::EINVAL,
+            "the flags do not match the type of the ns file"
+        );
+    }
+
+    apply(ns_file.ns().clone());
+    Ok(true)
+}
+
 fn set_uts_ns(
     builder: &mut NsProxyBuilder,
     target_ns: &Arc<UtsNamespace>,

test/initramfs/src/syscall/gvisor/Makefile

@@ -52,6 +52,7 @@ TESTS ?= \
 	sched_yield_test \
 	semaphore_test \
 	sendfile_test \
+	setns_test \
 	sigaction_test \
 	sigaltstack_test \
 	signalfd_test \

test/initramfs/src/syscall/gvisor/blocklists/setns_test

@@ -0,0 +1,2 @@
+SetnsTest.ChangeIPCNamespace
+SetnsTest.ChangePIDNamespace