cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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scm.c (3769B)

      1// SPDX-License-Identifier: GPL-2.0
      2#include <linux/module.h>
      3#include <linux/kernel.h>
      4#include <linux/string.h>
      5#include <linux/socket.h>
      6#include <linux/net.h>
      7#include <linux/fs.h>
      8#include <net/af_unix.h>
      9#include <net/scm.h>
     10#include <linux/init.h>
     11#include <linux/io_uring.h>
     12
     13#include "scm.h"
     14
     15unsigned int unix_tot_inflight;
     16EXPORT_SYMBOL(unix_tot_inflight);
     17
     18LIST_HEAD(gc_inflight_list);
     19EXPORT_SYMBOL(gc_inflight_list);
     20
     21DEFINE_SPINLOCK(unix_gc_lock);
     22EXPORT_SYMBOL(unix_gc_lock);
     23
     24struct sock *unix_get_socket(struct file *filp)
     25{
     26	struct sock *u_sock = NULL;
     27	struct inode *inode = file_inode(filp);
     28
     29	/* Socket ? */
     30	if (S_ISSOCK(inode->i_mode) && !(filp->f_mode & FMODE_PATH)) {
     31		struct socket *sock = SOCKET_I(inode);
     32		struct sock *s = sock->sk;
     33
     34		/* PF_UNIX ? */
     35		if (s && sock->ops && sock->ops->family == PF_UNIX)
     36			u_sock = s;
     37	} else {
     38		/* Could be an io_uring instance */
     39		u_sock = io_uring_get_socket(filp);
     40	}
     41	return u_sock;
     42}
     43EXPORT_SYMBOL(unix_get_socket);
     44
     45/* Keep the number of times in flight count for the file
     46 * descriptor if it is for an AF_UNIX socket.
     47 */
     48void unix_inflight(struct user_struct *user, struct file *fp)
     49{
     50	struct sock *s = unix_get_socket(fp);
     51
     52	spin_lock(&unix_gc_lock);
     53
     54	if (s) {
     55		struct unix_sock *u = unix_sk(s);
     56
     57		if (atomic_long_inc_return(&u->inflight) == 1) {
     58			BUG_ON(!list_empty(&u->link));
     59			list_add_tail(&u->link, &gc_inflight_list);
     60		} else {
     61			BUG_ON(list_empty(&u->link));
     62		}
     63		/* Paired with READ_ONCE() in wait_for_unix_gc() */
     64		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
     65	}
     66	user->unix_inflight++;
     67	spin_unlock(&unix_gc_lock);
     68}
     69
     70void unix_notinflight(struct user_struct *user, struct file *fp)
     71{
     72	struct sock *s = unix_get_socket(fp);
     73
     74	spin_lock(&unix_gc_lock);
     75
     76	if (s) {
     77		struct unix_sock *u = unix_sk(s);
     78
     79		BUG_ON(!atomic_long_read(&u->inflight));
     80		BUG_ON(list_empty(&u->link));
     81
     82		if (atomic_long_dec_and_test(&u->inflight))
     83			list_del_init(&u->link);
     84		/* Paired with READ_ONCE() in wait_for_unix_gc() */
     85		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
     86	}
     87	user->unix_inflight--;
     88	spin_unlock(&unix_gc_lock);
     89}
     90
     91/*
     92 * The "user->unix_inflight" variable is protected by the garbage
     93 * collection lock, and we just read it locklessly here. If you go
     94 * over the limit, there might be a tiny race in actually noticing
     95 * it across threads. Tough.
     96 */
     97static inline bool too_many_unix_fds(struct task_struct *p)
     98{
     99	struct user_struct *user = current_user();
    100
    101	if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
    102		return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
    103	return false;
    104}
    105
    106int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
    107{
    108	int i;
    109
    110	if (too_many_unix_fds(current))
    111		return -ETOOMANYREFS;
    112
    113	/*
    114	 * Need to duplicate file references for the sake of garbage
    115	 * collection.  Otherwise a socket in the fps might become a
    116	 * candidate for GC while the skb is not yet queued.
    117	 */
    118	UNIXCB(skb).fp = scm_fp_dup(scm->fp);
    119	if (!UNIXCB(skb).fp)
    120		return -ENOMEM;
    121
    122	for (i = scm->fp->count - 1; i >= 0; i--)
    123		unix_inflight(scm->fp->user, scm->fp->fp[i]);
    124	return 0;
    125}
    126EXPORT_SYMBOL(unix_attach_fds);
    127
    128void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
    129{
    130	int i;
    131
    132	scm->fp = UNIXCB(skb).fp;
    133	UNIXCB(skb).fp = NULL;
    134
    135	for (i = scm->fp->count-1; i >= 0; i--)
    136		unix_notinflight(scm->fp->user, scm->fp->fp[i]);
    137}
    138EXPORT_SYMBOL(unix_detach_fds);
    139
    140void unix_destruct_scm(struct sk_buff *skb)
    141{
    142	struct scm_cookie scm;
    143
    144	memset(&scm, 0, sizeof(scm));
    145	scm.pid  = UNIXCB(skb).pid;
    146	if (UNIXCB(skb).fp)
    147		unix_detach_fds(&scm, skb);
    148
    149	/* Alas, it calls VFS */
    150	/* So fscking what? fput() had been SMP-safe since the last Summer */
    151	scm_destroy(&scm);
    152	sock_wfree(skb);
    153}
    154EXPORT_SYMBOL(unix_destruct_scm);