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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Vasily Averin](/assets/img/avatar_default.png)
unix sockets allows to send file descriptors via SCM_RIGHTS type messages. Each such send call forces kernel to allocate up to 2Kb memory for struct scm_fp_list. It makes sense to account for them to restrict the host's memory consumption from inside the memcg-limited container. Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Signed-off-by: David S. Miller <davem@davemloft.net>
367 lines
8.5 KiB
C
367 lines
8.5 KiB
C
// 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, <kuznet@ms2.inr.ac.ru>
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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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