Fix Tramp's file-attributes cache

* lisp/net/tramp-adb.el (tramp-adb-handle-file-executable-p):
Check also for sticky bit.
(tramp-adb-handle-file-readable-p): Simplify.

* lisp/net/tramp-gvfs.el (tramp-gvfs-handle-file-executable-p):
Check also for sticky bit.  Force `file-attributes' check.

* lisp/net/tramp-sh.el (tramp-sh-handle-file-executable-p):
Check also for sticky bit.
(tramp-sh-handle-file-readable-p)
(tramp-sh-handle-file-writable-p): Simplify.

* lisp/net/tramp-sudoedit.el (tramp-sudoedit-handle-file-executable-p):
Check also for sticky bit.
(tramp-sudoedit-handle-file-readable-p)
(tramp-sudoedit-handle-file-writable-p): Simplify.

* lisp/net/tramp.el (tramp-use-file-attributes): Fix docstring.
(tramp-handle-file-readable-p, tramp-handle-file-writable-p):
Force `file-attributes' check.  Use `file-truename' for symbolic links.
(tramp-check-cached-permissions): New optional argument FORCE.
Fix symlink check.  Check also for sticky bit.  (Bug#77402)

* test/lisp/net/tramp-tests.el
(tramp-test20-file-modes-without-file-attributes)
(tramp-test21-file-links-without-file-attributes): New tests.

6 files changed, 54 insertions, 50 deletions

diff --git a/lisp/net/tramp-adb.el b/lisp/net/tramp-adb.el
index 1ecabd8165f..dee6b7899e9 100644
--- a/lisp/net/tramp-adb.el
+++ b/lisp/net/tramp-adb.el
@@ -480,11 +480,11 @@ Emacs dired can't find files."
     (with-tramp-file-property v localname "file-executable-p"
       ;; Examine `file-attributes' cache to see if request can be
       ;; satisfied without remote operation.
-      (if (tramp-use-file-attributes v)
-          (or (tramp-check-cached-permissions v ?x)
-              (tramp-check-cached-permissions v ?s))
-        (tramp-adb-send-command-and-check
-         v (format "test -x %s" (tramp-shell-quote-argument localname)))))))
+      (or (tramp-check-cached-permissions v ?x)
+          (tramp-check-cached-permissions v ?s)
+          (tramp-check-cached-permissions v ?t)
+          (tramp-adb-send-command-and-check
+           v (format "test -x %s" (tramp-shell-quote-argument localname)))))))
 
 (defun tramp-adb-handle-file-exists-p (filename)
   "Like `file-exists-p' for Tramp files."
@@ -498,10 +498,9 @@ Emacs dired can't find files."
     (with-tramp-file-property v localname "file-readable-p"
       ;; Examine `file-attributes' cache to see if request can be
       ;; satisfied without remote operation.
-      (if (tramp-use-file-attributes v)
-          (tramp-handle-file-readable-p filename)
-        (tramp-adb-send-command-and-check
-         v (format "test -r %s" (tramp-shell-quote-argument localname)))))))
+      (or (tramp-handle-file-readable-p filename)
+          (tramp-adb-send-command-and-check
+           v (format "test -r %s" (tramp-shell-quote-argument localname)))))))
 
 (defun tramp-adb-handle-file-writable-p (filename)
   "Like `file-writable-p' for Tramp files."
diff --git a/lisp/net/tramp-gvfs.el b/lisp/net/tramp-gvfs.el
index 3df69d79fce..9530aa3733a 100644
--- a/lisp/net/tramp-gvfs.el
+++ b/lisp/net/tramp-gvfs.el
@@ -1467,8 +1467,9 @@ If FILE-SYSTEM is non-nil, return file system attributes."
   "Like `file-executable-p' for Tramp files."
   (with-parsed-tramp-file-name (expand-file-name filename) nil
     (with-tramp-file-property v localname "file-executable-p"
-      (or (tramp-check-cached-permissions v ?x)
-          (tramp-check-cached-permissions v ?s)))))
+      (or (tramp-check-cached-permissions v ?x 'force)
+          (tramp-check-cached-permissions v ?s 'force)
+          (tramp-check-cached-permissions v ?t 'force)))))
 
 (defun tramp-gvfs-handle-file-name-all-completions (filename directory)
   "Like `file-name-all-completions' for Tramp files."
diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index ef4ddee8a53..4b770e95038 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -1783,10 +1783,10 @@ ID-FORMAT valid values are `string' and `integer'."
     (with-tramp-file-property v localname "file-executable-p"
       ;; Examine `file-attributes' cache to see if request can be
       ;; satisfied without remote operation.
-      (if (tramp-use-file-attributes v)
-          (or (tramp-check-cached-permissions v ?x)
-              (tramp-check-cached-permissions v ?s))
-        (tramp-run-test v "-x" localname)))))
+      (or (tramp-check-cached-permissions v ?x)
+          (tramp-check-cached-permissions v ?s)
+          (tramp-check-cached-permissions v ?t)
+          (tramp-run-test v "-x" localname)))))
 
 (defun tramp-sh-handle-file-readable-p (filename)
   "Like `file-readable-p' for Tramp files."
@@ -1794,9 +1794,8 @@ ID-FORMAT valid values are `string' and `integer'."
     (with-tramp-file-property v localname "file-readable-p"
       ;; Examine `file-attributes' cache to see if request can be
       ;; satisfied without remote operation.
-      (if (tramp-use-file-attributes v)
-          (tramp-handle-file-readable-p filename)
-        (tramp-run-test v "-r" localname)))))
+      (or (tramp-handle-file-readable-p filename)
+          (tramp-run-test v "-r" localname)))))
 
 ;; Functions implemented using the basic functions above.
 
@@ -1826,13 +1825,11 @@ ID-FORMAT valid values are `string' and `integer'."
       (if (file-exists-p filename)
           ;; Examine `file-attributes' cache to see if request can be
           ;; satisfied without remote operation.
-          (if (tramp-use-file-attributes v)
-              (tramp-check-cached-permissions v ?w)
-            (tramp-run-test v "-w" localname))
+          (or (tramp-check-cached-permissions v ?w)
+              (tramp-run-test v "-w" localname))
         ;; If file doesn't exist, check if directory is writable.
-        (and
-         (file-directory-p (file-name-directory filename))
-         (file-writable-p (file-name-directory filename)))))))
+        (and (file-directory-p (file-name-directory filename))
+             (file-writable-p (file-name-directory filename)))))))
 
 (defun tramp-sh-handle-file-ownership-preserved-p (filename &optional group)
   "Like `file-ownership-preserved-p' for Tramp files."
diff --git a/lisp/net/tramp-sudoedit.el b/lisp/net/tramp-sudoedit.el
index ff01eac5b93..59b4ea46b8c 100644
--- a/lisp/net/tramp-sudoedit.el
+++ b/lisp/net/tramp-sudoedit.el
@@ -479,11 +479,11 @@ the result will be a local, non-Tramp, file name."
     (with-tramp-file-property v localname "file-executable-p"
       ;; Examine `file-attributes' cache to see if request can be
       ;; satisfied without remote operation.
-      (if (tramp-use-file-attributes v)
-          (or (tramp-check-cached-permissions v ?x)
-              (tramp-check-cached-permissions v ?s))
-        (tramp-sudoedit-send-command
-         v "test" "-x" (file-name-unquote localname))))))
+      (or (tramp-check-cached-permissions v ?x)
+          (tramp-check-cached-permissions v ?s)
+          (tramp-check-cached-permissions v ?t)
+          (tramp-sudoedit-send-command
+           v "test" "-x" (file-name-unquote localname))))))
 
 (defun tramp-sudoedit-handle-file-exists-p (filename)
   "Like `file-exists-p' for Tramp files."
@@ -519,10 +519,9 @@ the result will be a local, non-Tramp, file name."
     (with-tramp-file-property v localname "file-readable-p"
       ;; Examine `file-attributes' cache to see if request can be
       ;; satisfied without remote operation.
-      (if (tramp-use-file-attributes v)
-          (tramp-handle-file-readable-p filename)
-        (tramp-sudoedit-send-command
-         v "test" "-r" (file-name-unquote localname))))))
+      (or (tramp-handle-file-readable-p filename)
+          (tramp-sudoedit-send-command
+           v "test" "-r" (file-name-unquote localname))))))
 
 (defun tramp-sudoedit-handle-set-file-modes (filename mode &optional flag)
   "Like `set-file-modes' for Tramp files."
@@ -604,10 +603,9 @@ the result will be a local, non-Tramp, file name."
       (if (file-exists-p filename)
           ;; Examine `file-attributes' cache to see if request can be
           ;; satisfied without remote operation.
-          (if (tramp-use-file-attributes v)
-              (tramp-check-cached-permissions v ?w)
-            (tramp-sudoedit-send-command
-             v "test" "-w" (file-name-unquote localname)))
+          (or (tramp-check-cached-permissions v ?w)
+              (tramp-sudoedit-send-command
+               v "test" "-w" (file-name-unquote localname)))
         ;; If file doesn't exist, check if directory is writable.
         (and
          (file-directory-p (file-name-directory filename))
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index ec8835c13f0..6c1a4ae7127 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -3509,7 +3509,7 @@ BODY is the backend specific code."
       nil)))
 
 (defcustom tramp-use-file-attributes t
-  "Whether to use \"file-attributes\" file property for check.
+  "Whether to use \"file-attributes\" connection property for check.
 This is relevant for read, write, and execute permissions.  On some file
 systems using NFS4_ACL, the permission string as returned from `stat' or
 `ls', is not sufficient to provide more fine-grained information.
@@ -4331,13 +4331,12 @@ Let-bind it when necessary.")
   "Like `file-readable-p' for Tramp files."
   (with-parsed-tramp-file-name (expand-file-name filename) nil
     (with-tramp-file-property v localname "file-readable-p"
-      (or (tramp-check-cached-permissions v ?r)
+      (or (tramp-check-cached-permissions v ?r 'force)
           ;; `tramp-check-cached-permissions' doesn't handle symbolic
           ;; links.
           (and-let* ((symlink (file-symlink-p filename))
                      ((stringp symlink))
-                     ((file-readable-p
-                       (concat (file-remote-p filename) symlink)))))))))
+                     ((file-readable-p (file-truename filename)))))))))
 
 (defun tramp-handle-file-regular-p (filename)
   "Like `file-regular-p' for Tramp files."
@@ -4431,7 +4430,12 @@ existing) are returned."
   (with-parsed-tramp-file-name (expand-file-name filename) nil
     (with-tramp-file-property v localname "file-writable-p"
       (if (file-exists-p filename)
-          (tramp-check-cached-permissions v ?w)
+          (or (tramp-check-cached-permissions v ?w 'force)
+              ;; `tramp-check-cached-permissions' doesn't handle
+              ;; symbolic links.
+              (and-let* ((symlink (file-symlink-p filename))
+                         ((stringp symlink))
+                         ((file-writable-p (file-truename filename))))))
         ;; If file doesn't exist, check if directory is writable.
         (and (file-directory-p (file-name-directory filename))
              (file-writable-p (file-name-directory filename)))))))
@@ -6424,23 +6428,24 @@ VEC is used for tracing."
       (when vec (tramp-message vec 7 "locale %s" (or locale "C")))
       (or locale "C"))))
 
-(defun tramp-check-cached-permissions (vec access)
+(defun tramp-check-cached-permissions (vec access &optional force)
   "Check `file-attributes' caches for VEC.
-Return t if according to the cache access type ACCESS is known to
-be granted."
+Return t if according to the cache access type ACCESS is known to be
+granted, if `tramp-use-file-attributes' mandates this.  If FORCE is
+non-nil, use connection property \"file-attributes\" mandatory."
   (when-let* ((offset (cond
                        ((eq ?r access) 1)
                        ((eq ?w access) 2)
                        ((eq ?x access) 3)
-                       ((eq ?s access) 3)))
+                       ((eq ?s access) 3)
+                       ((eq ?t access) 3)))
+              ((or force (tramp-use-file-attributes vec)))
               (file-attr (file-attributes (tramp-make-tramp-file-name vec)))
+              ;; Not a symlink.
+              ((not (stringp (file-attribute-type file-attr))))
               (remote-uid (tramp-get-remote-uid vec 'integer))
               (remote-gid (tramp-get-remote-gid vec 'integer)))
     (or
-     ;; Not a symlink.
-     (eq t (file-attribute-type file-attr))
-     (null (file-attribute-type file-attr)))
-    (or
      ;; World accessible.
      (eq access (aref (file-attribute-modes file-attr) (+ offset 6)))
      ;; User accessible and owned by user.
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index 605b26206c4..e22f1afc18b 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -4279,6 +4279,8 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
           (ignore-errors (delete-file tmp-name1))
           (ignore-errors (delete-file tmp-name2)))))))
 
+(tramp--test-deftest-without-file-attributes tramp-test20-file-modes)
+
 ;; Method "smb" could run into "NT_STATUS_REVISION_MISMATCH" error.
 (defmacro tramp--test-ignore-add-name-to-file-error (&rest body)
   "Run BODY, ignoring \"error with add-name-to-file\" file error."
@@ -4578,6 +4580,8 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
         (should (string-equal (file-truename dir1) (expand-file-name dir1)))
         (should (string-equal (file-truename dir2) (expand-file-name dir2)))))))
 
+(tramp--test-deftest-without-file-attributes tramp-test21-file-links)
+
 (ert-deftest tramp-test22-file-times ()
   "Check `set-file-times' and `file-newer-than-file-p'."
   (skip-unless (tramp--test-enabled))