From 0305b0abe4ada656462d575a5e0f0618b42def2d Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Tue, 23 Apr 2024 14:35:09 +0200
Subject: VFS: Fix reference count of file descriptors.

It appears that there was a race condition where the process got closed
before the server accepted the incoming request. Causing the file
descriptor to have "0" in the reference count but it would still be
given when calling accept.
---
 kernel/fs/devfs.c |  3 ++-
 kernel/fs/fifo.c  | 20 --------------------
 kernel/fs/fifo.h  |  1 -
 kernel/fs/tmpfs.c |  6 ++++++
 kernel/fs/vfs.c   |  4 +++-
 kernel/socket.c   |  5 +++--
 6 files changed, 14 insertions(+), 25 deletions(-)

(limited to 'kernel')

diff --git a/kernel/fs/devfs.c b/kernel/fs/devfs.c
index a3f13db..c25c996 100644
--- a/kernel/fs/devfs.c
+++ b/kernel/fs/devfs.c
@@ -84,7 +84,8 @@ void add_stdout(void) {
 }
 
 vfs_inode_t *devfs_mount(void) {
-  vfs_inode_t *root = kmalloc(sizeof(vfs_inode_t));
+  vfs_inode_t *root = kcalloc(1, sizeof(vfs_inode_t));
+  root->ref++;
   root->open = devfs_open;
   root->read = devfs_read;
   root->write = devfs_write;
diff --git a/kernel/fs/fifo.c b/kernel/fs/fifo.c
index a0a9248..5b01616 100644
--- a/kernel/fs/fifo.c
+++ b/kernel/fs/fifo.c
@@ -63,26 +63,6 @@ FIFO_FILE *create_fifo_object(void) {
   return n;
 }
 
-int create_fifo(void) {
-
-  vfs_fd_t *fd = kmalloc(sizeof(vfs_fd_t));
-  int fd_n;
-  assert(list_add(&current_task->file_descriptors, fd, &fd_n));
-
-  fd->flags = O_RDWR | O_NONBLOCK;
-  fd->inode = kmalloc(sizeof(vfs_inode_t));
-
-  fd->inode->internal_object = (void *)create_fifo_object();
-  fd->inode->open = NULL;
-  fd->inode->read = fifo_read;
-  fd->inode->write = fifo_write;
-  fd->inode->close = fifo_close;
-  fd->inode->get_vm_object = NULL;
-  fd->inode->is_open = 1;
-
-  return fd_n;
-}
-
 int fifo_write(u8 *buffer, u64 offset, u64 len, vfs_fd_t *fd) {
   (void)offset;
   FIFO_FILE *file = (FIFO_FILE *)fd->inode->internal_object;
diff --git a/kernel/fs/fifo.h b/kernel/fs/fifo.h
index 456b85d..450b9b5 100644
--- a/kernel/fs/fifo.h
+++ b/kernel/fs/fifo.h
@@ -14,7 +14,6 @@ struct S_FIFO_FILE {
   u8 can_write;
 };
 
-int create_fifo(void);
 FIFO_FILE *create_fifo_object(void);
 int fifo_object_write(u8 *buffer, u64 offset, u64 len, FIFO_FILE *file);
 int fifo_object_read(u8 *buffer, u64 offset, u64 len, FIFO_FILE *file);
diff --git a/kernel/fs/tmpfs.c b/kernel/fs/tmpfs.c
index e31a08e..3ef774c 100644
--- a/kernel/fs/tmpfs.c
+++ b/kernel/fs/tmpfs.c
@@ -58,12 +58,15 @@ void dual_pipe(int fd[2]) {
         vfs_create_fd(O_RDWR | O_NONBLOCK, 0, 0 /*is_tty*/, inode, &fd_ptrs[i]);
     assert(-1 != fd[i]);
   }
+
   vfs_inode_t *f_inode = fd_ptrs[0]->inode;
   vfs_inode_t *s_inode = fd_ptrs[1]->inode;
   tmp_inode *f_pipe = f_inode->internal_object;
   tmp_inode *s_pipe = s_inode->internal_object;
   f_pipe->read_inode = s_inode;
+  s_inode->ref++;
   s_pipe->read_inode = f_inode;
+  f_inode->ref++;
   f_pipe->is_closed = 0;
   s_pipe->is_closed = 0;
 }
@@ -89,12 +92,15 @@ void pipe(int fd[2]) {
     fd[i] = vfs_create_fd(O_RDWR, 0, 0 /*is_tty*/, inode, &fd_ptrs[i]);
     assert(-1 != fd[i]);
   }
+
   vfs_inode_t *f_inode = fd_ptrs[0]->inode;
   vfs_inode_t *s_inode = fd_ptrs[1]->inode;
   tmp_inode *f_pipe = f_inode->internal_object;
   tmp_inode *s_pipe = s_inode->internal_object;
   f_pipe->read_inode = s_inode;
+  s_inode->ref++;
   s_pipe->read_inode = f_inode;
+  f_inode->ref++;
   f_pipe->is_closed = 0;
   s_pipe->is_closed = 0;
 }
diff --git a/kernel/fs/vfs.c b/kernel/fs/vfs.c
index bcc0ce5..a55f78c 100644
--- a/kernel/fs/vfs.c
+++ b/kernel/fs/vfs.c
@@ -55,7 +55,7 @@ vfs_inode_t *vfs_create_inode(
   r->truncate = truncate;
   r->stat = stat;
   r->send_signal = send_signal;
-  r->ref = 1;
+  r->ref = 0;
   return r;
 }
 
@@ -415,11 +415,13 @@ int vfs_dup2(int org_fd, int new_fd) {
     assert(0);
     return -1;
   }
+  assert(1 <= orig->reference_count);
   if (!list_set(&current_task->file_descriptors, new_fd, orig)) {
     assert(0);
     return -1;
   }
   orig->reference_count++;
+  assert(2 <= orig->reference_count);
   return 1;
 }
 
diff --git a/kernel/socket.c b/kernel/socket.c
index 589d99a..d24e39c 100644
--- a/kernel/socket.c
+++ b/kernel/socket.c
@@ -240,7 +240,8 @@ int uds_open(const char *path) {
   s->ptr_socket_fd->inode->has_data = 1;
 
   s->incoming_fd = get_vfs_fd(fd[1], NULL);
-  // vfs_close(fd[1]);
+  s->incoming_fd->reference_count++;
+  vfs_close(fd[1]);
   return fd[0];
 }
 
@@ -263,7 +264,7 @@ int accept(int socket, struct sockaddr *address, socklen_t *address_len) {
 
   int index;
   assert(list_add(&current_task->file_descriptors, s->incoming_fd, &index));
-  s->incoming_fd->reference_count++;
+  assert(1 <= s->incoming_fd->reference_count);
   s->incoming_fd = NULL;
   //  for (char c; 0 < vfs_pread(s->fifo_fd, &c, 1, 0);)
   //    ;
-- 
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