| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* scm.c - Socket level control messages processing. |
| * |
| * Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> |
| * Alignment and value checking mods by Craig Metz |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/signal.h> |
| #include <linux/capability.h> |
| #include <linux/errno.h> |
| #include <linux/sched.h> |
| #include <linux/sched/user.h> |
| #include <linux/mm.h> |
| #include <linux/kernel.h> |
| #include <linux/stat.h> |
| #include <linux/socket.h> |
| #include <linux/file.h> |
| #include <linux/fcntl.h> |
| #include <linux/net.h> |
| #include <linux/interrupt.h> |
| #include <linux/netdevice.h> |
| #include <linux/security.h> |
| #include <linux/pid_namespace.h> |
| #include <linux/pid.h> |
| #include <linux/nsproxy.h> |
| #include <linux/slab.h> |
| #include <linux/errqueue.h> |
| #include <linux/io_uring.h> |
| |
| #include <linux/uaccess.h> |
| |
| #include <net/protocol.h> |
| #include <linux/skbuff.h> |
| #include <net/sock.h> |
| #include <net/compat.h> |
| #include <net/scm.h> |
| #include <net/cls_cgroup.h> |
| |
| |
| /* |
| * Only allow a user to send credentials, that they could set with |
| * setu(g)id. |
| */ |
| |
| static __inline__ int scm_check_creds(struct ucred *creds) |
| { |
| const struct cred *cred = current_cred(); |
| kuid_t uid = make_kuid(cred->user_ns, creds->uid); |
| kgid_t gid = make_kgid(cred->user_ns, creds->gid); |
| |
| if (!uid_valid(uid) || !gid_valid(gid)) |
| return -EINVAL; |
| |
| if ((creds->pid == task_tgid_vnr(current) || |
| ns_capable(task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) && |
| ((uid_eq(uid, cred->uid) || uid_eq(uid, cred->euid) || |
| uid_eq(uid, cred->suid)) || ns_capable(cred->user_ns, CAP_SETUID)) && |
| ((gid_eq(gid, cred->gid) || gid_eq(gid, cred->egid) || |
| gid_eq(gid, cred->sgid)) || ns_capable(cred->user_ns, CAP_SETGID))) { |
| return 0; |
| } |
| return -EPERM; |
| } |
| |
| static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) |
| { |
| int *fdp = (int*)CMSG_DATA(cmsg); |
| struct scm_fp_list *fpl = *fplp; |
| struct file **fpp; |
| int i, num; |
| |
| num = (cmsg->cmsg_len - sizeof(struct cmsghdr))/sizeof(int); |
| |
| if (num <= 0) |
| return 0; |
| |
| if (num > SCM_MAX_FD) |
| return -EINVAL; |
| |
| if (!fpl) |
| { |
| fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL_ACCOUNT); |
| if (!fpl) |
| return -ENOMEM; |
| *fplp = fpl; |
| fpl->count = 0; |
| fpl->max = SCM_MAX_FD; |
| fpl->user = NULL; |
| } |
| fpp = &fpl->fp[fpl->count]; |
| |
| if (fpl->count + num > fpl->max) |
| return -EINVAL; |
| |
| /* |
| * Verify the descriptors and increment the usage count. |
| */ |
| |
| for (i=0; i< num; i++) |
| { |
| int fd = fdp[i]; |
| struct file *file; |
| |
| if (fd < 0 || !(file = fget_raw(fd))) |
| return -EBADF; |
| /* don't allow io_uring files */ |
| if (io_uring_get_socket(file)) { |
| fput(file); |
| return -EINVAL; |
| } |
| *fpp++ = file; |
| fpl->count++; |
| } |
| |
| if (!fpl->user) |
| fpl->user = get_uid(current_user()); |
| |
| return num; |
| } |
| |
| void __scm_destroy(struct scm_cookie *scm) |
| { |
| struct scm_fp_list *fpl = scm->fp; |
| int i; |
| |
| if (fpl) { |
| scm->fp = NULL; |
| for (i=fpl->count-1; i>=0; i--) |
| fput(fpl->fp[i]); |
| free_uid(fpl->user); |
| kfree(fpl); |
| } |
| } |
| EXPORT_SYMBOL(__scm_destroy); |
| |
| int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) |
| { |
| struct cmsghdr *cmsg; |
| int err; |
| |
| for_each_cmsghdr(cmsg, msg) { |
| err = -EINVAL; |
| |
| /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ |
| /* The first check was omitted in <= 2.2.5. The reasoning was |
| that parser checks cmsg_len in any case, so that |
| additional check would be work duplication. |
| But if cmsg_level is not SOL_SOCKET, we do not check |
| for too short ancillary data object at all! Oops. |
| OK, let's add it... |
| */ |
| if (!CMSG_OK(msg, cmsg)) |
| goto error; |
| |
| if (cmsg->cmsg_level != SOL_SOCKET) |
| continue; |
| |
| switch (cmsg->cmsg_type) |
| { |
| case SCM_RIGHTS: |
| if (!sock->ops || sock->ops->family != PF_UNIX) |
| goto error; |
| err=scm_fp_copy(cmsg, &p->fp); |
| if (err<0) |
| goto error; |
| break; |
| case SCM_CREDENTIALS: |
| { |
| struct ucred creds; |
| kuid_t uid; |
| kgid_t gid; |
| if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) |
| goto error; |
| memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred)); |
| err = scm_check_creds(&creds); |
| if (err) |
| goto error; |
| |
| p->creds.pid = creds.pid; |
| if (!p->pid || pid_vnr(p->pid) != creds.pid) { |
| struct pid *pid; |
| err = -ESRCH; |
| pid = find_get_pid(creds.pid); |
| if (!pid) |
| goto error; |
| put_pid(p->pid); |
| p->pid = pid; |
| } |
| |
| err = -EINVAL; |
| uid = make_kuid(current_user_ns(), creds.uid); |
| gid = make_kgid(current_user_ns(), creds.gid); |
| if (!uid_valid(uid) || !gid_valid(gid)) |
| goto error; |
| |
| p->creds.uid = uid; |
| p->creds.gid = gid; |
| break; |
| } |
| default: |
| goto error; |
| } |
| } |
| |
| if (p->fp && !p->fp->count) |
| { |
| kfree(p->fp); |
| p->fp = NULL; |
| } |
| return 0; |
| |
| error: |
| scm_destroy(p); |
| return err; |
| } |
| EXPORT_SYMBOL(__scm_send); |
| |
| int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) |
| { |
| int cmlen = CMSG_LEN(len); |
| |
| if (msg->msg_flags & MSG_CMSG_COMPAT) |
| return put_cmsg_compat(msg, level, type, len, data); |
| |
| if (!msg->msg_control || msg->msg_controllen < sizeof(struct cmsghdr)) { |
| msg->msg_flags |= MSG_CTRUNC; |
| return 0; /* XXX: return error? check spec. */ |
| } |
| if (msg->msg_controllen < cmlen) { |
| msg->msg_flags |= MSG_CTRUNC; |
| cmlen = msg->msg_controllen; |
| } |
| |
| if (msg->msg_control_is_user) { |
| struct cmsghdr __user *cm = msg->msg_control_user; |
| |
| check_object_size(data, cmlen - sizeof(*cm), true); |
| |
| if (!user_write_access_begin(cm, cmlen)) |
| goto efault; |
| |
| unsafe_put_user(cmlen, &cm->cmsg_len, efault_end); |
| unsafe_put_user(level, &cm->cmsg_level, efault_end); |
| unsafe_put_user(type, &cm->cmsg_type, efault_end); |
| unsafe_copy_to_user(CMSG_USER_DATA(cm), data, |
| cmlen - sizeof(*cm), efault_end); |
| user_write_access_end(); |
| } else { |
| struct cmsghdr *cm = msg->msg_control; |
| |
| cm->cmsg_level = level; |
| cm->cmsg_type = type; |
| cm->cmsg_len = cmlen; |
| memcpy(CMSG_DATA(cm), data, cmlen - sizeof(*cm)); |
| } |
| |
| cmlen = min(CMSG_SPACE(len), msg->msg_controllen); |
| msg->msg_control += cmlen; |
| msg->msg_controllen -= cmlen; |
| return 0; |
| |
| efault_end: |
| user_write_access_end(); |
| efault: |
| return -EFAULT; |
| } |
| EXPORT_SYMBOL(put_cmsg); |
| |
| void put_cmsg_scm_timestamping64(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) |
| { |
| struct scm_timestamping64 tss; |
| int i; |
| |
| for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { |
| tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; |
| tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; |
| } |
| |
| put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_NEW, sizeof(tss), &tss); |
| } |
| EXPORT_SYMBOL(put_cmsg_scm_timestamping64); |
| |
| void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) |
| { |
| struct scm_timestamping tss; |
| int i; |
| |
| for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { |
| tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; |
| tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; |
| } |
| |
| put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_OLD, sizeof(tss), &tss); |
| } |
| EXPORT_SYMBOL(put_cmsg_scm_timestamping); |
| |
| static int scm_max_fds(struct msghdr *msg) |
| { |
| if (msg->msg_controllen <= sizeof(struct cmsghdr)) |
| return 0; |
| return (msg->msg_controllen - sizeof(struct cmsghdr)) / sizeof(int); |
| } |
| |
| void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) |
| { |
| struct cmsghdr __user *cm = |
| (__force struct cmsghdr __user *)msg->msg_control; |
| unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0; |
| int fdmax = min_t(int, scm_max_fds(msg), scm->fp->count); |
| int __user *cmsg_data = CMSG_USER_DATA(cm); |
| int err = 0, i; |
| |
| /* no use for FD passing from kernel space callers */ |
| if (WARN_ON_ONCE(!msg->msg_control_is_user)) |
| return; |
| |
| if (msg->msg_flags & MSG_CMSG_COMPAT) { |
| scm_detach_fds_compat(msg, scm); |
| return; |
| } |
| |
| for (i = 0; i < fdmax; i++) { |
| err = receive_fd_user(scm->fp->fp[i], cmsg_data + i, o_flags); |
| if (err < 0) |
| break; |
| } |
| |
| if (i > 0) { |
| int cmlen = CMSG_LEN(i * sizeof(int)); |
| |
| err = put_user(SOL_SOCKET, &cm->cmsg_level); |
| if (!err) |
| err = put_user(SCM_RIGHTS, &cm->cmsg_type); |
| if (!err) |
| err = put_user(cmlen, &cm->cmsg_len); |
| if (!err) { |
| cmlen = CMSG_SPACE(i * sizeof(int)); |
| if (msg->msg_controllen < cmlen) |
| cmlen = msg->msg_controllen; |
| msg->msg_control += cmlen; |
| msg->msg_controllen -= cmlen; |
| } |
| } |
| |
| if (i < scm->fp->count || (scm->fp->count && fdmax <= 0)) |
| msg->msg_flags |= MSG_CTRUNC; |
| |
| /* |
| * All of the files that fit in the message have had their usage counts |
| * incremented, so we just free the list. |
| */ |
| __scm_destroy(scm); |
| } |
| EXPORT_SYMBOL(scm_detach_fds); |
| |
| struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) |
| { |
| struct scm_fp_list *new_fpl; |
| int i; |
| |
| if (!fpl) |
| return NULL; |
| |
| new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), |
| GFP_KERNEL_ACCOUNT); |
| if (new_fpl) { |
| for (i = 0; i < fpl->count; i++) |
| get_file(fpl->fp[i]); |
| new_fpl->max = new_fpl->count; |
| new_fpl->user = get_uid(fpl->user); |
| } |
| return new_fpl; |
| } |
| EXPORT_SYMBOL(scm_fp_dup); |