scm: Don't use struct ucred in NETLINK_CB and struct scm_cookie.
Passing uids and gids on NETLINK_CB from a process in one user
namespace to a process in another user namespace can result in the
wrong uid or gid being presented to userspace. Avoid that problem by
passing kuids and kgids instead.
- define struct scm_creds for use in scm_cookie and netlink_skb_parms
that holds uid and gid information in kuid_t and kgid_t.
- Modify scm_set_cred to fill out scm_creds by heand instead of using
cred_to_ucred to fill out struct ucred. This conversion ensures
userspace does not get incorrect uid or gid values to look at.
- Modify scm_recv to convert from struct scm_creds to struct ucred
before copying credential values to userspace.
- Modify __scm_send to populate struct scm_creds on in the scm_cookie,
instead of just copying struct ucred from userspace.
- Modify netlink_sendmsg to copy scm_creds instead of struct ucred
into the NETLINK_CB.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/scm.h b/include/net/scm.h
index 7dc0854..456695f 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -12,6 +12,12 @@
*/
#define SCM_MAX_FD 253
+struct scm_creds {
+ u32 pid;
+ kuid_t uid;
+ kgid_t gid;
+};
+
struct scm_fp_list {
short count;
short max;
@@ -22,7 +28,7 @@
struct pid *pid; /* Skb credentials */
const struct cred *cred;
struct scm_fp_list *fp; /* Passed files */
- struct ucred creds; /* Skb credentials */
+ struct scm_creds creds; /* Skb credentials */
#ifdef CONFIG_SECURITY_NETWORK
u32 secid; /* Passed security ID */
#endif
@@ -49,7 +55,9 @@
{
scm->pid = get_pid(pid);
scm->cred = cred ? get_cred(cred) : NULL;
- cred_to_ucred(pid, cred, &scm->creds);
+ scm->creds.pid = pid_vnr(pid);
+ scm->creds.uid = cred ? cred->euid : INVALID_UID;
+ scm->creds.gid = cred ? cred->egid : INVALID_GID;
}
static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
@@ -112,8 +120,15 @@
return;
}
- if (test_bit(SOCK_PASSCRED, &sock->flags))
- put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(scm->creds), &scm->creds);
+ if (test_bit(SOCK_PASSCRED, &sock->flags)) {
+ struct user_namespace *current_ns = current_user_ns();
+ struct ucred ucreds = {
+ .pid = scm->creds.pid,
+ .uid = from_kuid_munged(current_ns, scm->creds.uid),
+ .gid = from_kgid_munged(current_ns, scm->creds.gid),
+ };
+ put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds);
+ }
scm_destroy_cred(scm);