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

[Paul Moore <paul@paul-moore.com>]

On Mon, Apr 20, 2020 at 5:36 PM Paul Moore <paul@paul-moore.com> 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: stable@vger.kernel.org
> Fixes: 756125289285 ("audit: always check the netlink payload length in audit_receive_msg()")
> Reported-by: syzbot+49e69b4d71a420ceda3e@syzkaller.appspotmail.com
> Signed-off-by: Paul Moore <paul@paul-moore.com>
> ---
>  kernel/audit.c |    3 +++
>  1 file changed, 3 insertions(+)

Merged into audit/stable-5.7; I'll send it up to Linus later this week.

> 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 */

-- 
paul moore
www.paul-moore.com


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