Audit: fix handling of 'strings' with NULL characters

currently audit_log_n_untrustedstring() uses audit_string_contains_control()
to check if the 'string' has any control characters.  If the 'string' has an
embedded NULL audit_string_contains_control() will return that the data has
no control characters and will then pass the string to audit_log_n_string
with the total length, not the length up to the first NULL.
audit_log_n_string() does a memcpy of the entire length and so the actual
audit record emitted may then contain a NULL and then whatever random memory
is after the NULL.

Since we want to log the entire octet stream (if we can't trust the data
to be a string we can't trust that a NULL isn't actually a part of it)
we should just consider NULL as a control character.  If the caller is
certain they want to stop at the first NULL they should be using
audit_log_untrustedstring.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/kernel/audit.c b/kernel/audit.c
index ce6d8ea3131e78136b3b50803c424c0fffbeb20a..fa3805516dffd546b4d0ebe95f1e44d6c3c1e7b7 100644 (file)
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1382,7 +1382,7 @@ void audit_log_n_string(struct audit_buffer *ab, const char *string,
 int audit_string_contains_control(const char *string, size_t len)
 {
        const unsigned char *p;
-       for (p = string; p < (const unsigned char *)string + len && *p; p++) {
+       for (p = string; p < (const unsigned char *)string + len; p++) {
                if (*p == '"' || *p < 0x21 || *p > 0x7e)
                        return 1;
        }