diff options
Diffstat (limited to 'net/core/scm.c')
| -rw-r--r-- | net/core/scm.c | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/net/core/scm.c b/net/core/scm.c new file mode 100644 index 00000000..611c5efd --- /dev/null +++ b/net/core/scm.c @@ -0,0 +1,345 @@ +/* scm.c - Socket level control messages processing. + * + * Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> + * Alignment and value checking mods by Craig Metz + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/module.h> +#include <linux/signal.h> +#include <linux/capability.h> +#include <linux/errno.h> +#include <linux/sched.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.h> +#include <linux/nsproxy.h> +#include <linux/slab.h> + +#include <asm/uaccess.h> + +#include <net/protocol.h> +#include <linux/skbuff.h> +#include <net/sock.h> +#include <net/compat.h> +#include <net/scm.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(); + + if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && + ((creds->uid == cred->uid || creds->uid == cred->euid || + creds->uid == cred->suid) || capable(CAP_SETUID)) && + ((creds->gid == cred->gid || creds->gid == cred->egid || + creds->gid == cred->sgid) || capable(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 - CMSG_ALIGN(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; + } + 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; + *fpp++ = file; + fpl->count++; + } + return num; +} + +void __scm_destroy(struct scm_cookie *scm) +{ + struct scm_fp_list *fpl = scm->fp; + int i; + + if (fpl) { + scm->fp = NULL; + if (current->scm_work_list) { + list_add_tail(&fpl->list, current->scm_work_list); + } else { + LIST_HEAD(work_list); + + current->scm_work_list = &work_list; + + list_add(&fpl->list, &work_list); + while (!list_empty(&work_list)) { + fpl = list_first_entry(&work_list, struct scm_fp_list, list); + + list_del(&fpl->list); + for (i=fpl->count-1; i>=0; i--) + fput(fpl->fp[i]); + kfree(fpl); + } + + current->scm_work_list = NULL; + } + } +} +EXPORT_SYMBOL(__scm_destroy); + +int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) +{ + struct cmsghdr *cmsg; + int err; + + for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) + { + 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: + if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) + goto error; + memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); + err = scm_check_creds(&p->creds); + if (err) + goto error; + + if (!p->pid || 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 || + (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.gid; + if (p->cred) + put_cred(p->cred); + p->cred = cred; + } + 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) +{ + struct cmsghdr __user *cm + = (__force struct cmsghdr __user *)msg->msg_control; + struct cmsghdr cmhdr; + int cmlen = CMSG_LEN(len); + int err; + + if (MSG_CMSG_COMPAT & msg->msg_flags) + return put_cmsg_compat(msg, level, type, len, data); + + if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { + 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; + } + cmhdr.cmsg_level = level; + cmhdr.cmsg_type = type; + cmhdr.cmsg_len = cmlen; + + err = -EFAULT; + if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) + goto out; + if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) + goto out; + cmlen = CMSG_SPACE(len); + if (msg->msg_controllen < cmlen) + cmlen = msg->msg_controllen; + msg->msg_control += cmlen; + msg->msg_controllen -= cmlen; + err = 0; +out: + return err; +} +EXPORT_SYMBOL(put_cmsg); + +void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) +{ + struct cmsghdr __user *cm + = (__force struct cmsghdr __user*)msg->msg_control; + + int fdmax = 0; + int fdnum = scm->fp->count; + struct file **fp = scm->fp->fp; + int __user *cmfptr; + int err = 0, i; + + if (MSG_CMSG_COMPAT & msg->msg_flags) { + scm_detach_fds_compat(msg, scm); + return; + } + + if (msg->msg_controllen > sizeof(struct cmsghdr)) + fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) + / sizeof(int)); + + if (fdnum < fdmax) + fdmax = fdnum; + + for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; + i++, cmfptr++) + { + int new_fd; + err = security_file_receive(fp[i]); + if (err) + break; + err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags + ? O_CLOEXEC : 0); + if (err < 0) + break; + new_fd = err; + err = put_user(new_fd, cmfptr); + if (err) { + put_unused_fd(new_fd); + break; + } + /* Bump the usage count and install the file. */ + get_file(fp[i]); + fd_install(new_fd, fp[i]); + } + + 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)); + msg->msg_control += cmlen; + msg->msg_controllen -= cmlen; + } + } + if (i < fdnum || (fdnum && 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; + } + return new_fpl; +} +EXPORT_SYMBOL(scm_fp_dup); |