diff options
Diffstat (limited to 'net/core/scm.c')
| -rw-r--r-- | net/core/scm.c | 366 |
1 files changed, 366 insertions, 0 deletions
diff --git a/net/core/scm.c b/net/core/scm.c new file mode 100644 index 000000000..3c7f16072 --- /dev/null +++ b/net/core/scm.c @@ -0,0 +1,366 @@ +// 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); + 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; + struct cmsghdr cmhdr; + + cmhdr.cmsg_level = level; + cmhdr.cmsg_type = type; + cmhdr.cmsg_len = cmlen; + if (copy_to_user(cm, &cmhdr, sizeof cmhdr) || + copy_to_user(CMSG_USER_DATA(cm), data, cmlen - sizeof(*cm))) + return -EFAULT; + } 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; +} +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); + 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); |