A path with a part over 255 bytes is refused, never a panic

std's statFile takes the kernel's ENAMETOOLONG for a bug (errnoBug), so a name, look, DumpDir or Save path with a part over 255 bytes panicked the editor (exec.kindOf via writeName, recentKeeps, dumpFailed). Every non-test statFile now goes through fs.statPath, which refuses such a name as NameTooLong first; fs.py drives long, looping, not-a-directory and not-ours paths through name, look, DumpDir, Dump and Save.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 16 insertions, 1 deletions

diff --git a/src/fs.zig b/src/fs.zig
index 5fd1fd4e..753a4446 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -159,7 +159,7 @@ pub fn osHandle(p: *pardes.Pardes, req: Req) Reply {
     const stat = stat: {
         pardes.turn.yield();
         defer pardes.turn.back();
-        break :stat std.Io.Dir.cwd().statFile(io, path, .{}) catch return Reply.fail(req.tag, E.NOENT);
+        break :stat statPath(io, path, .{}) catch return Reply.fail(req.tag, E.NOENT);
     };
     const attr: Reply.Attr = .{ .name = if (req.node == os_root) "os" else std.fs.path.basename(path), .node = req.node, .dir = stat.kind == .directory, .size = stat.size, .mode = if (stat.kind == .directory) 0o755 else 0o644, .mtime = std.math.cast(u32, stat.mtime.toSeconds()) orelse 0 };
     switch (req.op) {
@@ -622,6 +622,21 @@ pub fn isVirtual(path: []const u8) bool {
         std.mem.eql(u8, path, "/n") or std.mem.startsWith(u8, path, "/n/");
 }
 
+/// std's `statFile`, but a name with a part over 255 bytes is NameTooLong:
+/// std's own takes the kernel's ENAMETOOLONG for that for a bug and panics
+/// (Io.Threaded dirStatFileLinux), and such a name comes from anyone who
+/// writes one to `name`, `look` or DumpDir.
+pub fn statPath(io: std.Io, path: []const u8, options: std.Io.Dir.StatFileOptions) !std.Io.File.Stat {
+    var parts = std.mem.tokenizeScalar(u8, path, '/');
+    while (parts.next()) |part| if (part.len > 255) return error.NameTooLong;
+    return std.Io.Dir.cwd().statFile(io, path, options);
+}
+
+test "a path with a part over 255 bytes is NameTooLong, never a panic" {
+    const long = "/tmp/" ++ "x" ** 300 ++ "/f";
+    try std.testing.expectError(error.NameTooLong, statPath(std.testing.io, long, .{}));
+}
+
 pub fn localPath(path: []const u8) ?[]const u8 {
     if (std.mem.eql(u8, path, "/n/os")) return "/";
     if (std.mem.startsWith(u8, path, "/n/os/")) return path[5..];