patch 9.0.1848: [security] buffer-overflow in vim_regsub_both()

Problem:  buffer-overflow in vim_regsub_both()
Solution: Check remaining space

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

src/ex_cmds.c

@@ -4651,6 +4651,9 @@ ex_substitute(exarg_T *eap)
 		mch_memmove(new_end, sub_firstline + copycol, (size_t)copy_len);
 		new_end += copy_len;
 
+		if (new_start_len - copy_len < sublen)
+		    sublen = new_start_len - copy_len - 1;
+
 #ifdef FEAT_EVAL
 		++textlock;
 #endif

src/regexp.c

@@ -2051,7 +2051,8 @@ vim_regsub_both(
 	// "flags & REGSUB_COPY" != 0.
 	if (copy)
 	{
-	    if (eval_result[nested] != NULL)
+	    if (eval_result[nested] != NULL &&
+		    STRLEN(eval_result[nested]) < destlen)
 	    {
 		STRCPY(dest, eval_result[nested]);
 		dst += STRLEN(eval_result[nested]);

src/testdir/crash/vim_regsub_both

@@ -0,0 +1,10 @@
+fu R()
+sil!norm0z=
+endf
+cal R()
+s/\%')/\=R()
+d
+no0 normyynore sm:vs0@vvvvvvvvvvse()dir(¼Xtest=csd{so88
+vs
+0scr
+so

src/testdir/test_crash.vim

@@ -6,7 +6,7 @@ CheckScreendump
 
 func Test_crash1()
   " The following used to crash Vim
-  let opts = #{wait_for_ruler: 0}
+  let opts = #{wait_for_ruler: 0, rows: 20}
   let args = ' -u NONE -i NONE -n -e -s -S '
   let buf = RunVimInTerminal(args .. ' crash/poc_huaf1', opts)
   call VerifyScreenDump(buf, 'Test_crash_01', {})
@@ -22,4 +22,13 @@ func Test_crash1()
 
 endfunc
 
+func Test_crash2()
+  " The following used to crash Vim
+  let opts = #{wait_for_ruler: 0, rows: 20}
+  let args = ' -u NONE -i NONE -n -e -s -S '
+  let buf = RunVimInTerminal(args .. ' crash/vim_regsub_both', opts)
+  call VerifyScreenDump(buf, 'Test_crash_01', {})
+  exe buf .. "bw!"
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1848,
 /**/
     1847,
 /**/