All in kernel users of %n in format strings have now been removed and
the %n directive is ignored. Remove the handling of %n so that it is
treated the same as any other invalid format string directive. Keep a
warning in place to deter new instances of %n in format strings.
Signed-off-by: Ryan Mallon <rmal...@gmail.com>
Acked-by: Kees Cook <keesc...@chromium.org>
---
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 10909c5..7c4c207 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -364,7 +364,6 @@ enum format_type {
FORMAT_TYPE_SHORT,
FORMAT_TYPE_UINT,
FORMAT_TYPE_INT,
- FORMAT_TYPE_NRCHARS,
FORMAT_TYPE_SIZE_T,
FORMAT_TYPE_PTRDIFF
};
@@ -1512,10 +1511,6 @@ qualifier:
return fmt - start;
/* skip alnum */
- case 'n':
- spec->type = FORMAT_TYPE_NRCHARS;
- return ++fmt - start;
-
case '%':
spec->type = FORMAT_TYPE_PERCENT_CHAR;
return ++fmt - start;
@@ -1538,6 +1533,15 @@ qualifier:
case 'u':
break;
+ case 'n':
+ /*
+ * Since %n poses a greater security risk than utility, treat
+ * it as an invalid format specifier. Warn about its use so
+ * that new instances don't get added.
+ */
+ WARN_ONCE(1, "Please remove ignored %%n in '%s'\n", fmt);
+ /* Fall-through */
+
default:
spec->type = FORMAT_TYPE_INVALID;
return fmt - start;
@@ -1711,20 +1715,6 @@ int vsnprintf(char *buf, size_t size, const char *fmt,
va_list args)
++str;
break;
- case FORMAT_TYPE_NRCHARS: {
- /*
- * Since %n poses a greater security risk than
- * utility, ignore %n and skip its argument.
- */
- void *skip_arg;
-
- WARN_ONCE(1, "Please remove ignored %%n in '%s'\n",
- old_fmt);
-
- skip_arg = va_arg(args, void *);
- break;
- }
-
default:
switch (spec.type) {
case FORMAT_TYPE_LONG_LONG:
@@ -1999,19 +1989,6 @@ do {
\
fmt++;
break;
- case FORMAT_TYPE_NRCHARS: {
- /* skip %n 's argument */
- u8 qualifier = spec.qualifier;
- void *skip_arg;
- if (qualifier == 'l')
- skip_arg = va_arg(args, long *);
- else if (_tolower(qualifier) == 'z')
- skip_arg = va_arg(args, size_t *);
- else
- skip_arg = va_arg(args, int *);
- break;
- }
-
default:
switch (spec.type) {
@@ -2170,10 +2147,6 @@ int bstr_printf(char *buf, size_t size, const char *fmt,
const u32 *bin_buf)
++str;
break;
- case FORMAT_TYPE_NRCHARS:
- /* skip */
- break;
-
default: {
unsigned long long num;
--
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