audit: format user messages to size of MAX_AUDIT_MESSAGE_LENGTH

Messages of type AUDIT_USER_TTY were being formatted to 1024 octets,
truncating messages approaching MAX_AUDIT_MESSAGE_LENGTH (8970 octets).

Set the formatting to 8560 characters, given maximum estimates for prefix and
suffix budgets.

See the problem discussion:
https://www.redhat.com/archives/linux-audit/2009-January/msg00030.html

And the new size rationale:
https://www.redhat.com/archives/linux-audit/2013-September/msg00016.html

Test ~8k messages with:
auditctl -m "$(for i in $(seq -w 001 820);do echo -n "${i}0______";done)"

Reported-by: LC Bruzenak <lenny@magitekltd.com>
Reported-by: Justin Stephenson <jstephen@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index 91e53d04b6a9..dd63d2f978d5 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -715,7 +715,8 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                         }
                         audit_log_common_recv_msg(&ab, msg_type);
                         if (msg_type != AUDIT_USER_TTY)
-                                audit_log_format(ab, " msg='%.1024s'",
+                                audit_log_format(ab, " msg='%.*s'",
+                                                 AUDIT_MESSAGE_TEXT_MAX,
                                                  (char *)data);
                         else {
                                 int size;