/pager takes one directory an open, as pty/run takes one line: a second line, in the same write or the next, is refused EINVAL

Through a mount `printf 'a\nb\n' > pager` arrives a line a write, so the
second asked for another +Pager on the same open, its answer replacing
the first. An open that asked already refuses another.

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

1 files changed, 14 insertions, 4 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 554333bb..4fb5bf41 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -656,8 +656,11 @@ pub fn writePager(p: *Pardes, req: Req) Reply {
     p.fs.results_len = 0;
     var it = Messages.init(p, req.data);
     const line = it.next() orelse "";
-    // Words 9ns maps back to EINVAL (`invalid`), as every refusal here.
-    if (it.next() != null) return tree.failText(req.tag, E.INVAL, "pager: invalid write: one directory a write");
+    // Words 9ns maps back to EINVAL (`invalid`), as every refusal here. One
+    // directory an open, as pty/run takes one line: through a mount
+    // `printf 'a\nb\n'` comes a line a write, and the second is refused.
+    const asked_before = if (tree.openOf(p, req)) |o| o.results.wrote else false;
+    if (it.next() != null or asked_before) return tree.failText(req.tag, E.INVAL, "pager: invalid write: one directory an open");
     // `~` is home, and `/tmp/../etc` is `/etc`: the +Pager is named in the
     // directory it is, as any other pane's name is.
     var home_buf: [4096]u8 = undefined;
@@ -4071,12 +4074,19 @@ test "pager answers its +Pager on the open that asked, whatever another client e
     try testing.expectEqual(E.INVAL, call(p, .{ .tag = 6, .op = .write, .node = pager, .handle = asked, .data = "relative\n" }).errno());
     try testing.expectEqualStrings("", call(p, .{ .tag = 7, .op = .read, .node = pager, .handle = asked, .size = 64 }).bytes);
     // Resolved: `/tmp/../tmp/.` is /tmp's +Pager, the one made above.
-    try testing.expectEqual(Status.ok, call(p, .{ .tag = 8, .op = .write, .node = pager, .handle = asked, .data = "/tmp/../tmp/.\n" }).reply.status);
-    try testing.expectEqualStrings(want, call(p, .{ .tag = 9, .op = .read, .node = pager, .handle = asked, .size = 64 }).bytes);
+    const again = call(p, .{ .tag = 8, .op = .open, .node = pager, .omode = 2 }).reply.handle;
+    try testing.expectEqual(Status.ok, call(p, .{ .tag = 8, .op = .write, .node = pager, .handle = again, .data = "/tmp/../tmp/.\n" }).reply.status);
+    try testing.expectEqualStrings(want, call(p, .{ .tag = 9, .op = .read, .node = pager, .handle = again, .size = 64 }).bytes);
+    _ = call(p, .{ .tag = 9, .op = .release, .node = pager, .handle = again });
     // One that may not be written is refused, permission denied.
     try testing.expectEqual(E.PERM, wr(p, pager, "/proc/1\n").errno());
     // One directory a write, absolute, and there.
     try testing.expectEqual(E.INVAL, wr(p, pager, "/a\n/b\n").errno());
+    // A second line on an open that asked already, as a mount sends two.
+    const twice = call(p, .{ .tag = 20, .op = .open, .node = pager, .omode = 2 }).reply.handle;
+    try testing.expectEqual(Status.ok, call(p, .{ .tag = 21, .op = .write, .node = pager, .handle = twice, .data = "/tmp\n" }).reply.status);
+    try testing.expectEqual(E.INVAL, call(p, .{ .tag = 22, .op = .write, .node = pager, .handle = twice, .data = "/tmp\n" }).errno());
+    _ = call(p, .{ .tag = 23, .op = .release, .node = pager, .handle = twice });
     const relative = wr(p, pager, "relative\n");
     try testing.expectEqual(E.INVAL, relative.errno());
     try testing.expectEqualStrings("pager: invalid directory \"relative\": must be absolute", relative.reply.ename);