Some inotify cleanup

This catches some problems with integer overflow and races
that I noticed in inotify.c after reviewing the changes
installed to fix Bug#26126.
* src/fns.c, src/lisp.h (equal_no_quit): Now extern.
* src/inotify.c (aspect_to_inotifymask):
Check for cycles and for improper lists.
(make_lispy_mask, lispy_mask_match_p): Remove.
All callers changed to use INTEGER_TO_CONS and CONS_TO_INTEGER.
(inotifyevent_to_event, add_watch):
Don’t assume watch descriptors and cookies fit in fixnums.
(add_watch): Use assoc_no_quit, not Fassoc.
Avoid integer overflow in (very!) long-running processes where
the Emacs watch ID could overflow.  Avoid some duplicate code.
(find_descriptor): New function.
(remove_descriptor): First arg is now the returned value from
find_descriptor, rather than the descriptor.  This way, the
value can be removed without calling Fdelete, which might quit.
Wait until the end (when watch_list is consistent) before signaling
any errors.
(remove_watch, inotify_callback):
Use find_descriptor to avoid the need for Fdelete.
(inotify_callback): Use simpler tests for ioctl failure.
Free temporary buffer if signaled, and put it on the stack if small.
Use ssize_t to index through read results, to avoid a cast.
(valid_watch_descriptor): New function, with a tighter check.
(Finotify_rm_watch, Finotify_valid_p): Use it.
(Finotify_valid_p): Use assoc_no_quit and ass_no_quit instead
of Fassoc.  Do not assume the first assoc succeeds.
* test/src/inotify-tests.el (inotify-valid-p-simple):
Add inotify-valid-p tests, some of which dump core without
the fixes noted above.

1 files changed, 9 insertions, 0 deletions

diff --git a/test/src/inotify-tests.el b/test/src/inotify-tests.el
index f30aecc9c4f..987e1fc0777 100644
--- a/test/src/inotify-tests.el
+++ b/test/src/inotify-tests.el
@@ -28,6 +28,13 @@
 (declare-function inotify-add-watch "inotify.c" (file-name aspect callback))
 (declare-function inotify-rm-watch "inotify.c" (watch-descriptor))
 
+(ert-deftest inotify-valid-p-simple ()
+  "Simple tests for `inotify-valid-p'."
+  (skip-unless (featurep 'inotify))
+  (should-not (inotify-valid-p 0))
+  (should-not (inotify-valid-p nil))
+  (should-not (inotify-valid-p '(0 . 0))))
+
 ;; (ert-deftest filewatch-file-watch-aspects-check ()
 ;;   "Test whether `file-watch' properly checks the aspects."
 ;;   (let ((temp-file (make-temp-file "filewatch-aspects")))
@@ -56,7 +63,9 @@
               (insert "Foo\n"))
             (read-event nil nil 5)
             (should (> events 0)))
+        (should (inotify-valid-p wd))
         (inotify-rm-watch wd)
+        (should-not (inotify-valid-p wd))
         (delete-file temp-file)))))
 
 (provide 'inotify-tests)