Route VFS permissions through COW handlers

2 files changed, 13 insertions, 11 deletions

diff --git a/src/src/fuseconnector.cpp b/src/src/fuseconnector.cpp
index 8b7d206..238ce13 100644
--- a/src/src/fuseconnector.cpp
+++ b/src/src/fuseconnector.cpp
@@ -329,6 +329,12 @@ void wrap_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
   MO2_TRY_REPLY(req, "fsync", ino, EIO)
 }
 
+void wrap_access(fuse_req_t req, fuse_ino_t ino, int mask) noexcept
+{
+  try { mo2_access(req, ino, mask); }
+  MO2_TRY_REPLY(req, "access", ino, EIO)
+}
+
 void wrap_statfs(fuse_req_t req, fuse_ino_t ino) noexcept
 {
   try { mo2_statfs(req, ino); }
@@ -449,6 +455,7 @@ void setupFuseOps(struct fuse_lowlevel_ops* ops)
   ops->releasedir  = wrap_releasedir;
   ops->flush       = wrap_flush;
   ops->fsync       = wrap_fsync;
+  ops->access      = wrap_access;
   ops->statfs      = wrap_statfs;
   ops->getlk       = wrap_getlk;
   ops->setlk       = wrap_setlk;
@@ -461,8 +468,6 @@ void setupFuseOps(struct fuse_lowlevel_ops* ops)
   ops->setxattr    = wrap_setxattr;
   ops->removexattr = wrap_removexattr;
   ops->ioctl       = wrap_ioctl;
-  // access handler removed: default_permissions mount option lets the kernel
-  // handle permission checks in-kernel, eliminating access() round-trips.
 }
 
 }  // namespace
@@ -662,7 +667,7 @@ bool FuseConnector::mount(
   // kernel reads don't fit.  1MB is the safe ceiling.
   std::vector<std::string> argvStorage = {
       "mo2fuse", "-o", "fsname=mo2linux", "-o", "noatime",
-      "-o", "default_permissions", "-o", "max_read=1048576"};
+      "-o", "max_read=1048576"};
   std::fprintf(stderr, "[VFS] libfuse=%s headers=%d.%d\n",
                fuse_pkgversion(), FUSE_MAJOR_VERSION, FUSE_MINOR_VERSION);
 
diff --git a/src/src/vfs/mo2filesystem.cpp b/src/src/vfs/mo2filesystem.cpp
index 377ce93..0f6d2a4 100644
--- a/src/src/vfs/mo2filesystem.cpp
+++ b/src/src/vfs/mo2filesystem.cpp
@@ -1082,9 +1082,8 @@ void fillStatForDir(struct stat* st, fuse_ino_t ino, uid_t uid, gid_t gid)
 mode_t regularFileVfsMode(mode_t sourceMode)
 {
   mode_t mode = sourceMode != 0 ? sourceMode : static_cast<mode_t>(0644);
-  // The merged VFS is copy-on-write. Existing files from the base game or mods
-  // must still pass the kernel's default_permissions write check so mo2_open()
-  // can materialize them into staging instead of failing before userspace.
+  // The merged VFS is copy-on-write, so expose source files as writable even
+  // when their physical base-game or mod files are read-only.
   mode |= S_IRUSR | S_IWUSR;
   return mode;
 }
@@ -3655,11 +3654,9 @@ void mo2_access(fuse_req_t req, fuse_ino_t ino, int mask)
       return;
     }
 
-    // W_OK: only allow for files we can write to (non-backing, non-directory)
-    if ((mask & W_OK) != 0 && (node->is_directory || node->file_info.is_backing)) {
-      fuse_reply_err(req, EACCES);
-      return;
-    }
+    // The merged filesystem is writable even when the winning source is a
+    // read-only base-game or mod file: mutations are redirected through COW.
+    // Directories must likewise permit creation of staged children.
   }
 
   // X_OK on regular files: check real file permissions