commit eec0c2b3a4cfab93dd8d4adaa60638d47a2bbc8a
author Christian Brabandt <cb@256bit.org> Tue Nov 28 22:03:48 2023 +0100
committer Christian Brabandt <cb@256bit.org> Fri Dec 01 18:58:50 2023 +0100
tree 2f60c6c3095b52818325cbd6c92dcb293f8c8727
parent 9cc95aa0d8f52bb0c906ca13297ce3a2ba615f2b

patch 9.0.2140: [security]: use-after-free in win-enter

Problem:  [security]: use-after-free in win-enter
Solution: validate window pointer before calling win_enter()

win_goto() may stop visual mode, if it is active. However, this may in
turn trigger the ModeChanged autocommand, which could potentially free
the wp pointer which was valid before now became stale and points to now
freed memory.

So before calling win_enter(), let's verify one more time, that the
wp pointer still points to a valid window structure.

Reported by @henices, thanks!

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/crash/poc_win_enter_ext

diff --git a/src/testdir/crash/poc_win_enter_ext b/src/testdir/crash/poc_win_enter_ext
new file mode 100644
index 0000000..73f53b5
--- /dev/null
+++ b/src/testdir/crash/poc_win_enter_ext
Binary files differ

src/testdir/test_crash.vim

diff --git a/src/testdir/test_crash.vim b/src/testdir/test_crash.vim
index b093b05..11c5f4e 100644
--- a/src/testdir/test_crash.vim
+++ b/src/testdir/test_crash.vim
@@ -128,6 +128,13 @@
     \ '  && echo "crash 1: [OK]" > '.. result .. "\<cr>")
   call TermWait(buf, 150)
 
+  let file = 'crash/poc_win_enter_ext'
+  let cmn_args = "%s -u NONE -i NONE -n -e -s -S %s -c ':qa!'"
+  let args = printf(cmn_args, vim, file)
+  call term_sendkeys(buf, args ..
+    \ '  && echo "crash 2: [OK]" >> '.. result .. "\<cr>")
+  call TermWait(buf, 350)
+
   " clean up
   exe buf .. "bw!"
 
@@ -135,6 +142,7 @@
 
   let expected = [
       \ 'crash 1: [OK]',
+      \ 'crash 2: [OK]',
       \ ]
 
   call assert_equal(expected, getline(1, '$'))

src/version.c

diff --git a/src/version.c b/src/version.c
index 3fc23c1..e32e5c0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2140,
+/**/
     2139,
 /**/
     2138,

src/window.c

diff --git a/src/window.c b/src/window.c
index 0f4363b..be010dc 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5013,6 +5013,7 @@
  * Go to another window.
  * When jumping to another buffer, stop Visual mode.  Do this before
  * changing windows so we can yank the selection into the '*' register.
+ * (note: this may trigger ModeChanged autocommand!)
  * When jumping to another window on the same buffer, adjust its cursor
  * position to keep the same Visual area.
  */
@@ -5039,10 +5040,15 @@
     }
 
     if (wp->w_buffer != curbuf)
+	// careful: triggers ModeChanged autocommand
 	reset_VIsual_and_resel();
     else if (VIsual_active)
 	wp->w_cursor = curwin->w_cursor;
 
+    // autocommand may have made wp invalid
+    if (!win_valid(wp))
+	return;
+
 #ifdef FEAT_GUI
     need_mouse_correct = TRUE;
 #endif