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