On Mon, Apr 20, 2020 at 5:56 PM Richard Guy Briggs <[email protected]> wrote: > On 2020-04-20 17:36, Paul Moore wrote: > > Commit 756125289285 ("audit: always check the netlink payload length > > in audit_receive_msg()") fixed a number of missing message length > > checks, but forgot to check the length of userspace generated audit > > records. The good news is that you need CAP_AUDIT_WRITE to submit > > userspace audit records, which is generally only given to trusted > > processes, so the impact should be limited. > > > > Cc: [email protected] > > Fixes: 756125289285 ("audit: always check the netlink payload length in > > audit_receive_msg()") > > Reported-by: [email protected] > > Signed-off-by: Paul Moore <[email protected]> > > --- > > kernel/audit.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/kernel/audit.c b/kernel/audit.c > > index b69c8b460341..87f31bf1f0a0 100644 > > --- a/kernel/audit.c > > +++ b/kernel/audit.c > > @@ -1326,6 +1326,9 @@ static int audit_receive_msg(struct sk_buff *skb, > > struct nlmsghdr *nlh) > > case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2: > > if (!audit_enabled && msg_type != AUDIT_USER_AVC) > > return 0; > > + /* exit early if there isn't at least one character to print > > */ > > + if (data_len < 2) > > + return -EINVAL; > > Don't we want to issue the record even if the message is empty? If a > len of 1 is passed in, it will properly set str[0] = '\0' and str points > to a location with a null that prints nothing between the single quotes > of "msg=''". So, I think that should be "if (data_len < 1)". > > Am I missing something?
I've got no problem with allowing an empty message so long as there is a valid use for such a message. Can anyone think of a valid reason for having an empty userspace generated record? -- paul moore www.paul-moore.com -- Linux-audit mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-audit
