161 lines
3.9 KiB
C
161 lines
3.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/socket.h>
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#include <linux/net.h>
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#include <linux/fs.h>
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#include <net/af_unix.h>
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#include <net/scm.h>
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#include <linux/init.h>
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#include <linux/io_uring.h>
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#include "scm.h"
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unsigned int unix_tot_inflight;
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EXPORT_SYMBOL(unix_tot_inflight);
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LIST_HEAD(gc_inflight_list);
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EXPORT_SYMBOL(gc_inflight_list);
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DEFINE_SPINLOCK(unix_gc_lock);
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EXPORT_SYMBOL(unix_gc_lock);
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struct sock *unix_get_socket(struct file *filp)
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{
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struct sock *u_sock = NULL;
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struct inode *inode = file_inode(filp);
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/* Socket ? */
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if (S_ISSOCK(inode->i_mode) && !(filp->f_mode & FMODE_PATH)) {
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struct socket *sock = SOCKET_I(inode);
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struct sock *s = sock->sk;
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/* PF_UNIX ? */
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if (s && sock->ops && sock->ops->family == PF_UNIX)
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u_sock = s;
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} else {
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/* Could be an io_uring instance */
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u_sock = io_uring_get_socket(filp);
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}
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return u_sock;
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}
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EXPORT_SYMBOL(unix_get_socket);
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/* Keep the number of times in flight count for the file
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* descriptor if it is for an AF_UNIX socket.
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*/
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void unix_inflight(struct user_struct *user, struct file *fp)
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{
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struct sock *s = unix_get_socket(fp);
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spin_lock(&unix_gc_lock);
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if (s) {
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struct unix_sock *u = unix_sk(s);
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if (atomic_long_inc_return(&u->inflight) == 1) {
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BUG_ON(!list_empty(&u->link));
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list_add_tail(&u->link, &gc_inflight_list);
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} else {
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BUG_ON(list_empty(&u->link));
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}
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/* Paired with READ_ONCE() in wait_for_unix_gc() */
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WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
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}
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WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
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spin_unlock(&unix_gc_lock);
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}
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void unix_notinflight(struct user_struct *user, struct file *fp)
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{
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struct sock *s = unix_get_socket(fp);
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spin_lock(&unix_gc_lock);
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if (s) {
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struct unix_sock *u = unix_sk(s);
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BUG_ON(!atomic_long_read(&u->inflight));
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BUG_ON(list_empty(&u->link));
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if (atomic_long_dec_and_test(&u->inflight))
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list_del_init(&u->link);
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/* Paired with READ_ONCE() in wait_for_unix_gc() */
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WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
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}
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WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
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spin_unlock(&unix_gc_lock);
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}
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/*
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* The "user->unix_inflight" variable is protected by the garbage
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* collection lock, and we just read it locklessly here. If you go
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* over the limit, there might be a tiny race in actually noticing
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* it across threads. Tough.
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*/
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static inline bool too_many_unix_fds(struct task_struct *p)
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{
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struct user_struct *user = current_user();
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if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE)))
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return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
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return false;
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}
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int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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{
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int i;
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if (too_many_unix_fds(current))
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return -ETOOMANYREFS;
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/*
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* Need to duplicate file references for the sake of garbage
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* collection. Otherwise a socket in the fps might become a
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* candidate for GC while the skb is not yet queued.
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*/
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UNIXCB(skb).fp = scm_fp_dup(scm->fp);
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if (!UNIXCB(skb).fp)
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return -ENOMEM;
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for (i = scm->fp->count - 1; i >= 0; i--)
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unix_inflight(scm->fp->user, scm->fp->fp[i]);
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return 0;
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}
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EXPORT_SYMBOL(unix_attach_fds);
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void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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{
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int i;
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scm->fp = UNIXCB(skb).fp;
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UNIXCB(skb).fp = NULL;
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for (i = scm->fp->count-1; i >= 0; i--)
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unix_notinflight(scm->fp->user, scm->fp->fp[i]);
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}
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EXPORT_SYMBOL(unix_detach_fds);
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void unix_destruct_scm(struct sk_buff *skb)
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{
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struct scm_cookie scm;
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memset(&scm, 0, sizeof(scm));
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scm.pid = UNIXCB(skb).pid;
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if (UNIXCB(skb).fp)
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unix_detach_fds(&scm, skb);
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/* Alas, it calls VFS */
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/* So fscking what? fput() had been SMP-safe since the last Summer */
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scm_destroy(&scm);
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sock_wfree(skb);
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}
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EXPORT_SYMBOL(unix_destruct_scm);
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void io_uring_destruct_scm(struct sk_buff *skb)
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{
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unix_destruct_scm(skb);
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}
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EXPORT_SYMBOL(io_uring_destruct_scm);
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