audit: ignore terminating NUL in AUDIT_USER_TTY messages

AUDIT_USER_TTY, like all other messages sent from user-space, is sent
NUL-terminated.  Unlike other user-space audit messages, which come only
from trusted sources, AUDIT_USER_TTY messages are processed using
audit_log_n_untrustedstring().

This patch modifies AUDIT_USER_TTY handling to ignore the trailing NUL
and use the "quoted_string" representation of the message if possible.

Signed-off-by: Miloslav Trmac <mitr@redhat.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Steve Grubb <sgrubb@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index fa3805516dff..5560390cb0f5 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -766,6 +766,9 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 
                                 audit_log_format(ab, " msg=");
                                 size = nlmsg_len(nlh);
+                                if (size > 0 &&
+                                    ((unsigned char *)data)[size - 1] == '\0')
+                                        size--;
                                 audit_log_n_untrustedstring(ab, data, size);
                         }
                         audit_set_pid(ab, pid);