symlink: handle_open() detects symlink creation

added check in handle_open() to avoid calling CREATE/OPEN when we're creating a symlink:

if (args->disposition == FILE_CREATE &&
    args->access_mask == (FILE_WRITE_ATTRIBUTES | SYNCHRONIZE | DELETE) &&
    args->access_mode == 0 &&
    args->create_opts & FILE_OPEN_REPARSE_POINT)

these are the open arguments we get from the CreateSymbolicLink() syscall.  by avoiding the call to CREATE/OPEN on handle_open(), we save ourselves from having to REMOVE the file before creating the symlink

added a check to handle_symlink() in case the file was actually created on open (an application could open the file with different arguments, and send the FSCTL_SET_REPARSE_POINT manually), and removes the file first

Signed-off-by: Casey Bodley <cbodley@citi.umich.edu>

daemon/open.c

@@ -274,7 +274,35 @@ int handle_open(nfs41_upcall *upcall)
         state->type = info.type;
     } else if (status != ERROR_FILE_NOT_FOUND)
         goto out_free_state;
-    if (do_lookup(state->type, args->access_mask, args->disposition)) {
+    
+    /* XXX: this is a hard-coded check for the open arguments we see from
+     * the CreateSymbolicLink() system call.  we respond to this by deferring
+     * the CREATE until we get the upcall to set the symlink.  this approach
+     * is troublesome for two reasons:
+     * -an application might use these exact arguments to create a normal
+     *   file, and we would return success without actually creating it
+     * -an application could create a symlink by sending the FSCTL to set
+     *   the reparse point manually, and their open might be different.  in
+     *   this case we'd create the file on open, and need to remove it
+     *   before creating the symlink */
+    if (args->disposition == FILE_CREATE &&
+        args->access_mask == (FILE_WRITE_ATTRIBUTES | SYNCHRONIZE | DELETE) &&
+        args->access_mode == 0 &&
+        args->create_opts & FILE_OPEN_REPARSE_POINT) {
+        /* fail if the file already exists */
+        uint32_t create;
+        status = map_disposition_2_nfsopen(args->disposition, status,
+            &create, &upcall->last_error);
+        if (status)
+            goto out_free_state;
+
+        /* defer the call to CREATE until we get the symlink set upcall */
+        dprintf(1, "trying to create a symlink, deferring create\n");
+
+        /* because of WRITE_ATTR access, be prepared for a setattr upcall;
+         * will crash if the superblock is null, so use the parent's */
+        state->file.fh.superblock = state->parent.fh.superblock;
+    } else if (do_lookup(state->type, args->access_mask, args->disposition)) {
         if (status) {
             dprintf(1, "nfs41_lookup failed with %d\n", status);
             goto out_free_state;

daemon/symlink.c

@@ -188,6 +188,12 @@ int handle_symlink(nfs41_upcall *upcall)
     int status = NO_ERROR;
 
     if (args->set) {
+        if (state->file.fh.len) {
+            /* the check in handle_open() didn't catch that we're creating
+             * a symlink, so we have to remove the file it already created */
+            nfs41_remove(state->session, &state->parent, &state->file.name);
+        }
+
         /* create the symlink */
         status = nfs41_create(state->session, NF4LNK, 0777,
             args->target_set, &state->parent, &state->file);

daemon/util.c

@@ -311,6 +311,7 @@ int nfs_to_windows_error(int status, int default_error)
     case NFS4ERR_SYMLINK:
     case NFS4ERR_WRONG_TYPE:    return ERROR_INVALID_PARAMETER;
 
+    case NFS4ERR_NOFILEHANDLE:
     case NFS4ERR_OLD_STATEID:
     case NFS4ERR_BAD_STATEID:
     case NFS4ERR_ADMIN_REVOKED: return ERROR_FILE_INVALID;

sys/nfs41_driver.c

@@ -3638,6 +3638,7 @@ static NTSTATUS map_setfile_error(DWORD error)
     case ERROR_FILE_NOT_FOUND:          return STATUS_OBJECT_NAME_NOT_FOUND;
     case ERROR_PATH_NOT_FOUND:          return STATUS_OBJECT_PATH_NOT_FOUND;
     case ERROR_ACCESS_DENIED:           return STATUS_ACCESS_DENIED;
+    case ERROR_FILE_INVALID:            return STATUS_FILE_INVALID;
     case ERROR_NOT_SAME_DEVICE:         return STATUS_NOT_SAME_DEVICE;
     case ERROR_NOT_SUPPORTED:           return STATUS_NOT_IMPLEMENTED;
     case ERROR_NETWORK_ACCESS_DENIED:   return STATUS_NETWORK_ACCESS_DENIED;