Quoting Eric W. Biederman (ebied...@xmission.com):
>
> Start capturing not only the userspace pid, uid and gid values of the
> sending process but also the struct pid and struct cred of the sending
> process as well.
>
> This is in preparation for properly supporting SCM_CREDENTIALS for
> sockets that have different uid and/or pid namespaces at the different
> ends.
>
> Signed-off-by: Eric W. Biederman <ebied...@xmission.com>
> ---
> include/net/scm.h | 28 ++++++++++++++++++++++++----
> net/core/scm.c | 24 ++++++++++++++++++++++++
> 2 files changed, 48 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/scm.h b/include/net/scm.h
> index 17d9d2e..3165650 100644
> --- a/include/net/scm.h
> +++ b/include/net/scm.h
> @@ -19,6 +19,8 @@ struct scm_fp_list {
> };
>
> struct scm_cookie {
> + struct pid *pid; /* Skb credentials */
> + const struct cred *cred;
> struct scm_fp_list *fp; /* Passed files */
> struct ucred creds; /* Skb credentials */
> #ifdef CONFIG_SECURITY_NETWORK
> @@ -42,8 +44,27 @@ static __inline__ void unix_get_peersec_dgram(struct
> socket *sock, struct scm_co
> { }
> #endif /* CONFIG_SECURITY_NETWORK */
>
> +static __inline__ void scm_set_cred(struct scm_cookie *scm,
> + struct pid *pid, const struct cred *cred)
> +{
> + scm->pid = get_pid(pid);
> + scm->cred = get_cred(cred);
> + cred_to_ucred(pid, cred, &scm->creds);
> +}
> +
> +static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
> +{
> + put_pid(scm->pid);
> + scm->pid = NULL;
> +
> + if (scm->cred)
> + put_cred(scm->cred);
> + scm->cred = NULL;
> +}
> +
> static __inline__ void scm_destroy(struct scm_cookie *scm)
> {
> + scm_destroy_cred(scm);
> if (scm && scm->fp)
> __scm_destroy(scm);
> }
> @@ -51,10 +72,7 @@ static __inline__ void scm_destroy(struct scm_cookie *scm)
> static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
> struct scm_cookie *scm)
> {
> - struct task_struct *p = current;
> - scm->creds.uid = current_uid();
> - scm->creds.gid = current_gid();
> - scm->creds.pid = task_tgid_vnr(p);
> + scm_set_cred(scm, task_tgid(current), current_cred());
> scm->fp = NULL;
> unix_get_peersec_dgram(sock, scm);
> if (msg->msg_controllen <= 0)
> @@ -96,6 +114,8 @@ static __inline__ void scm_recv(struct socket *sock,
> struct msghdr *msg,
> if (test_bit(SOCK_PASSCRED, &sock->flags))
> put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(scm->creds),
> &scm->creds);
>
> + scm_destroy_cred(scm);
> +
> scm_passec(sock, msg, scm);
>
> if (!scm->fp)
> diff --git a/net/core/scm.c b/net/core/scm.c
> index b88f6f9..681c976 100644
> --- a/net/core/scm.c
> +++ b/net/core/scm.c
> @@ -170,6 +170,30 @@ int __scm_send(struct socket *sock, struct msghdr *msg,
> struct scm_cookie *p)
> err = scm_check_creds(&p->creds);
> if (err)
> goto error;
> +
I think this hunk needs to be documented. I.e. given that scm_send()
will call scm_set_cred() before calling __scm_send, I don't see how
these conditions could happen? If the condition can legitimately
happen, then given all of the pid_t vs struct pid and 'cred' vs. 'creds'
in these two hunks, I think a comment over each would be nice.
> + if (pid_vnr(p->pid) != p->creds.pid) {
> + struct pid *pid;
> + err = -ESRCH;
> + pid = find_get_pid(p->creds.pid);
> + if (!pid)
> + goto error;
> + put_pid(p->pid);
> + p->pid = pid;
> + }
> +
> + if ((p->cred->euid != p->creds.uid) ||
> + (p->cred->egid != p->creds.gid)) {
> + struct cred *cred;
> + err = -ENOMEM;
> + cred = prepare_creds();
> + if (!cred)
> + goto error;
> +
> + cred->uid = cred->euid = p->creds.uid;
> + cred->gid = cred->egid = p->creds.uid;
> + put_cred(p->cred);
> + p->cred = cred;
> + }
> break;
> default:
> goto error;
> --
> 1.6.5.2.143.g8cc62
>
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