Re: [PATCH] audit: check the length of userspace generated audit records

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: stable(a)vger.kernel.org Fixes: 756125289285 ("audit: always check the netlink payload length in audit_receive_msg()") Reported-by: syzbot+49e69b4d71a420ceda3e(a)syzkaller.appspotmail.com Signed-off-by: Paul Moore <paul(a)paul-moore.com&gt; --- 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; err = audit_filter(msg_type, AUDIT_FILTER_USER); if (err == 1) { /* match or error */