From ac19a7e0e7c55551df1410be0a19422b1c36a72b Mon Sep 17 00:00:00 2001
From: Ruihan Li <lrh2000@pku.edu.cn>
Date: Thu, 15 Aug 2024 13:17:36 +0800
Subject: [PATCH] Fix race conditions in UNIX socket `listen()`

---
 .../src/net/socket/unix/stream/listener.rs        | 15 ++++++++-------
 .../src/net/socket/unix/stream/socket.rs          |  9 ++++++---
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/kernel/aster-nix/src/net/socket/unix/stream/listener.rs b/kernel/aster-nix/src/net/socket/unix/stream/listener.rs
index c479de8ac..3d746c870 100644
--- a/kernel/aster-nix/src/net/socket/unix/stream/listener.rs
+++ b/kernel/aster-nix/src/net/socket/unix/stream/listener.rs
@@ -16,9 +16,9 @@ pub(super) struct Listener {
 }
 
 impl Listener {
-    pub(super) fn new(addr: UnixSocketAddrBound, backlog: usize) -> Result<Self> {
-        let backlog = BACKLOG_TABLE.add_backlog(addr, backlog)?;
-        Ok(Self { backlog })
+    pub(super) fn new(addr: UnixSocketAddrBound, backlog: usize) -> Self {
+        let backlog = BACKLOG_TABLE.add_backlog(addr, backlog).unwrap();
+        Self { backlog }
     }
 
     pub(super) fn addr(&self) -> &UnixSocketAddrBound {
@@ -78,21 +78,22 @@ impl BacklogTable {
         }
     }
 
-    fn add_backlog(&self, addr: UnixSocketAddrBound, backlog: usize) -> Result<Arc<Backlog>> {
+    fn add_backlog(&self, addr: UnixSocketAddrBound, backlog: usize) -> Option<Arc<Backlog>> {
         let inode = {
             let UnixSocketAddrBound::Path(_, ref dentry) = addr else {
                 todo!()
             };
             create_keyable_inode(dentry)
         };
+        let new_backlog = Arc::new(Backlog::new(addr, backlog));
 
         let mut backlog_sockets = self.backlog_sockets.write();
         if backlog_sockets.contains_key(&inode) {
-            return_errno_with_message!(Errno::EADDRINUSE, "the addr is already used");
+            return None;
         }
-        let new_backlog = Arc::new(Backlog::new(addr, backlog));
         backlog_sockets.insert(inode, new_backlog.clone());
-        Ok(new_backlog)
+
+        Some(new_backlog)
     }
 
     fn get_backlog(&self, addr: &UnixSocketAddrBound) -> Result<Arc<Backlog>> {
diff --git a/kernel/aster-nix/src/net/socket/unix/stream/socket.rs b/kernel/aster-nix/src/net/socket/unix/stream/socket.rs
index eb9337296..53c51ff26 100644
--- a/kernel/aster-nix/src/net/socket/unix/stream/socket.rs
+++ b/kernel/aster-nix/src/net/socket/unix/stream/socket.rs
@@ -232,7 +232,9 @@ impl Socket for UnixStreamSocket {
     }
 
     fn listen(&self, backlog: usize) -> Result<()> {
-        let addr = match &*self.state.read() {
+        let mut state = self.state.write();
+
+        let addr = match &*state {
             State::Init(init) => init
                 .addr()
                 .ok_or(Error::with_message(
@@ -248,8 +250,9 @@ impl Socket for UnixStreamSocket {
             }
         };
 
-        let listener = Listener::new(addr, backlog)?;
-        *self.state.write() = State::Listen(listener);
+        let listener = Listener::new(addr, backlog);
+        *state = State::Listen(listener);
+
         Ok(())
     }