patch 9.1.1003: [security]: heap-buffer-overflow with visual mode

Problem:  [security]: heap-buffer-overflow with visual mode when
          using :all, causing Vim trying to access beyond end-of-line
          (gandalf)
Solution: Reset visual mode on :all, validate position in gchar_pos()
          and charwise_block_prep()

This fixes CVE-2025-22134

Github Advisory:
https://github.com/vim/vim/security/advisories/GHSA-5rgf-26wj-48v8

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/arglist.c

@@ -1258,6 +1258,10 @@ do_arg_all(
 
     tabpage_T *new_lu_tp = curtab;
 
+    // Stop Visual mode, the cursor and "VIsual" may very well be invalid after
+    // switching to another buffer.
+    reset_VIsual_and_resel();
+
     // Try closing all windows that are not in the argument list.
     // Also close windows that are not full width;
     // When 'hidden' or "forceit" set the buffer becomes hidden.

src/misc1.c

@@ -543,11 +543,15 @@ plines_m_win(win_T *wp, linenr_T first, linenr_T last, int max)
 gchar_pos(pos_T *pos)
 {
     char_u	*ptr;
+    int		ptrlen;
 
     // When searching columns is sometimes put at the end of a line.
     if (pos->col == MAXCOL)
 	return NUL;
+    ptrlen = ml_get_len(pos->lnum);
     ptr = ml_get_pos(pos);
+    if (pos->col > ptrlen)
+	return NUL;
     if (has_mbyte)
 	return (*mb_ptr2char)(ptr);
     return (int)*ptr;

src/ops.c

@@ -2586,6 +2586,7 @@ charwise_block_prep(
     colnr_T startcol = 0, endcol = MAXCOL;
     colnr_T cs, ce;
     char_u *p;
+    int	plen = ml_get_len(lnum);
 
     p = ml_get(lnum);
     bdp->startspaces = 0;
@@ -2646,7 +2647,7 @@ charwise_block_prep(
     else
 	bdp->textlen = endcol - startcol + inclusive;
     bdp->textcol = startcol;
-    bdp->textstart = p + startcol;
+    bdp->textstart = startcol <= plen ? p + startcol : p;
 }
 
 /*

src/testdir/test_visual.vim

@@ -470,7 +470,7 @@ func Test_Visual_Block()
 	      \ "\t{",
 	      \ "\t}"], getline(1, '$'))
 
-  close!
+  bw!
 endfunc
 
 " Test for 'p'ut in visual block mode
@@ -1080,7 +1080,7 @@ func Test_star_register()
 
   delmarks < >
   call assert_fails('*yank', 'E20:')
-  close!
+  bw!
 endfunc
 
 " Test for changing text in visual mode with 'exclusive' selection
@@ -1096,7 +1096,7 @@ func Test_exclusive_selection()
   call assert_equal('l      one', getline(1))
   set virtualedit&
   set selection&
-  close!
+  bw!
 endfunc
 
 " Test for starting linewise visual with a count.
@@ -1153,7 +1153,7 @@ func Test_visual_inner_block()
   8,9d
   call cursor(5, 1)
   call assert_beeps('normal ViBiB')
-  close!
+  bw!
 endfunc
 
 func Test_visual_put_in_block()
@@ -2760,4 +2760,22 @@ func Test_visual_block_exclusive_selection_adjusted()
   set selection&vim
 endfunc
 
+" the following caused a Heap-Overflow, because Vim was accessing outside of a
+" line end
+func Test_visual_pos_buffer_heap_overflow()
+  set virtualedit=all
+  args Xa Xb
+  all
+  call setline(1, ['', '', ''])
+  call cursor(3, 1)
+  wincmd w
+  call setline(1, 'foobar')
+  normal! $lv0
+  all
+  call setreg('"', 'baz')
+  normal! [P
+  set virtualedit=
+  bw! Xa Xb
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1003,
 /**/
     1002,
 /**/