lib/os: fdtable: add locking to posix api

Added locking to posix read(), write(), close()
for additional protection.

In read() missing lock would create uneven calls to locking
mechanism in sockets.c after k_condvar_wait().
That results in socket lock not ever being unlocked

Signed-off-by: Daniel Nejezchleb <[email protected]>

Author: dnejezchleb

lib/os/fdtable.c

@@ -224,21 +224,37 @@ int z_alloc_fd(void *obj, const struct fd_op_vtable *vtable)
 
 ssize_t read(int fd, void *buf, size_t sz)
 {
+	ssize_t res;
+
 	if (_check_fd(fd) < 0) {
 		return -1;
 	}
 
-	return fdtable[fd].vtable->read(fdtable[fd].obj, buf, sz);
+	(void)k_mutex_lock(&fdtable[fd].lock, K_FOREVER);
+
+	res = fdtable[fd].vtable->read(fdtable[fd].obj, buf, sz);
+
+	k_mutex_unlock(&fdtable[fd].lock);
+
+	return res;
 }
 FUNC_ALIAS(read, _read, ssize_t);
 
 ssize_t write(int fd, const void *buf, size_t sz)
 {
+	ssize_t res;
+
 	if (_check_fd(fd) < 0) {
 		return -1;
 	}
 
-	return fdtable[fd].vtable->write(fdtable[fd].obj, buf, sz);
+	(void)k_mutex_lock(&fdtable[fd].lock, K_FOREVER);
+
+	res = fdtable[fd].vtable->write(fdtable[fd].obj, buf, sz);
+
+	k_mutex_unlock(&fdtable[fd].lock);
+
+	return res;
 }
 FUNC_ALIAS(write, _write, ssize_t);
 
@@ -250,8 +266,12 @@ int close(int fd)
 		return -1;
 	}
 
+	(void)k_mutex_lock(&fdtable[fd].lock, K_FOREVER);
+
 	res = fdtable[fd].vtable->close(fdtable[fd].obj);
 
+	k_mutex_unlock(&fdtable[fd].lock);
+
 	z_free_fd(fd);
 
 	return res;