patch 9.1.0689: [security]: buffer-overflow in do_search() with 'rightleft'

Problem:  buffer-overflow in do_search() with 'rightleft'
          (SuyueGuo)
Solution: after reversing the text (which allocates a new buffer),
          re-calculate the text length

Github Advisory:
https://github.com/vim/vim/security/advisories/GHSA-v2x2-cjcg-f9jm

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

src/search.c

@@ -1548,6 +1548,7 @@ do_search(
 			{
 			    vim_free(msgbuf);
 			    msgbuf = r;
+			    msgbuflen = STRLEN(msgbuf);
 			    // move reversed text to beginning of buffer
 			    while (*r != NUL && *r == ' ')
 				r++;

src/testdir/test_crash.vim

@@ -150,6 +150,13 @@ func Test_crash1_2()
     \ ' ; echo "crash 4: [OK]" >> '.. result .. "\<cr>")
   call TermWait(buf, 150)
 
+  let file = 'crash/reverse_text_overflow'
+  let cmn_args = "%s -u NONE -i NONE -n -X -m -n -e -s -S %s -c ':qa!'"
+  let args = printf(cmn_args, vim, file)
+  call term_sendkeys(buf, args ..
+    \ ' ; echo "crash 5: [OK]" >> '.. result .. "\<cr>")
+  call TermWait(buf, 150)
+
   " clean up
   exe buf .. "bw!"
   exe "sp " .. result
@@ -158,6 +165,7 @@ func Test_crash1_2()
       \ 'crash 2: [OK]',
       \ 'crash 3: [OK]',
       \ 'crash 4: [OK]',
+      \ 'crash 5: [OK]',
       \ ]
 
   call assert_equal(expected, getline(1, '$'))
@@ -201,6 +209,7 @@ func Test_crash1_3()
   let args = printf(cmn_args, vim, file)
   call term_sendkeys(buf, args)
   call TermWait(buf, 150)
+  call delete('Untitled')
 
   let file = 'crash/nullpointer'
   let cmn_args = "%s -u NONE -i NONE -n -e -s -S %s -c ':qa!'\<cr>"

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    689,
 /**/
     688,
 /**/