commit f6d39c31d2177549a986d170e192d8351bd571e2
author Bram Moolenaar <Bram@vim.org> Tue Aug 16 17:50:38 2022 +0100
committer Bram Moolenaar <Bram@vim.org> Tue Aug 16 17:50:38 2022 +0100
tree 88571362c680104807bb5201a8e1f52871b8de39
parent 948a3894d98f5e2a6e7fc57189fe9c2a5919eebf

patch 9.0.0220: invalid memory access with for loop over NULL string

Problem:    Invalid memory access with for loop over NULL string.
Solution:   Make sure mb_ptr2len() consistently returns zero for NUL.

src/globals.h

diff --git a/src/globals.h b/src/globals.h
index 1fadc74..21fabdb 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1035,7 +1035,8 @@
  * (DBCS).
  * The value is set in mb_init();
  */
-// length of char in bytes, including following composing chars
+// Length of char in bytes, including any following composing chars.
+// NUL has length zero.
 EXTERN int (*mb_ptr2len)(char_u *p) INIT(= latin_ptr2len);
 
 // idem, with limit on string length

src/mbyte.c

diff --git a/src/mbyte.c b/src/mbyte.c
index 941411b..73065c7 100644
--- a/src/mbyte.c
+++ b/src/mbyte.c
@@ -1077,24 +1077,28 @@
 }
 
 /*
- * mb_ptr2len() function pointer.
- * Get byte length of character at "*p" but stop at a NUL.
- * For UTF-8 this includes following composing characters.
- * Returns 0 when *p is NUL.
+ * Get byte length of character at "*p".  Returns zero when "*p" is NUL.
+ * Used for mb_ptr2len() when 'encoding' latin.
  */
     int
 latin_ptr2len(char_u *p)
 {
- return MB_BYTE2LEN(*p);
+    return *p == NUL ? 0 : 1;
 }
 
+/*
+ * Get byte length of character at "*p".  Returns zero when "*p" is NUL.
+ * Used for mb_ptr2len() when 'encoding' DBCS.
+ */
     static int
-dbcs_ptr2len(
-    char_u	*p)
+dbcs_ptr2len(char_u *p)
 {
     int		len;
 
-    // Check if second byte is not missing.
+    if (*p == NUL)
+	return 0;
+
+    // if the second byte is missing the length is 1
     len = MB_BYTE2LEN(*p);
     if (len == 2 && p[1] == NUL)
 	len = 1;
@@ -2105,6 +2109,7 @@
 /*
  * Return the number of bytes the UTF-8 encoding of the character at "p" takes.
  * This includes following composing characters.
+ * Returns zero for NUL.
  */
     int
 utfc_ptr2len(char_u *p)

src/testdir/test_eval_stuff.vim

diff --git a/src/testdir/test_eval_stuff.vim b/src/testdir/test_eval_stuff.vim
index c63082e..313d791 100644
--- a/src/testdir/test_eval_stuff.vim
+++ b/src/testdir/test_eval_stuff.vim
Binary files differ

src/version.c

diff --git a/src/version.c b/src/version.c
index 3aff052..a6293e0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    220,
+/**/
     219,
 /**/
     218,