Home Home > GIT Browse
summaryrefslogtreecommitdiff
blob: 8c40f2b323924d304111b7b8981e9bb209722d5b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
// SPDX-License-Identifier: GPL-2.0
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <linux/fs.h>
#include <net/af_unix.h>
#include <net/scm.h>
#include <linux/init.h>

#include "scm.h"

unsigned int unix_tot_inflight;
EXPORT_SYMBOL(unix_tot_inflight);

LIST_HEAD(gc_inflight_list);
EXPORT_SYMBOL(gc_inflight_list);

DEFINE_SPINLOCK(unix_gc_lock);
EXPORT_SYMBOL(unix_gc_lock);

struct sock *unix_get_socket(struct file *filp)
{
	struct sock *u_sock = NULL;
	struct inode *inode = file_inode(filp);

	/* Socket ? */
	if (S_ISSOCK(inode->i_mode) && !(filp->f_mode & FMODE_PATH)) {
		struct socket *sock = SOCKET_I(inode);
		struct sock *s = sock->sk;

		/* PF_UNIX ? */
		if (s && sock->ops && sock->ops->family == PF_UNIX)
			u_sock = s;
	} else {
		/* Could be an io_uring instance */
		u_sock = io_uring_get_socket(filp);
	}
	return u_sock;
}
EXPORT_SYMBOL(unix_get_socket);

/* Keep the number of times in flight count for the file
 * descriptor if it is for an AF_UNIX socket.
 */
void unix_inflight(struct user_struct *user, struct file *fp)
{
	struct sock *s = unix_get_socket(fp);

	spin_lock(&unix_gc_lock);

	if (s) {
		struct unix_sock *u = unix_sk(s);

		if (atomic_long_inc_return(&u->inflight) == 1) {
			BUG_ON(!list_empty(&u->link));
			list_add_tail(&u->link, &gc_inflight_list);
		} else {
			BUG_ON(list_empty(&u->link));
		}
		unix_tot_inflight++;
	}
	user->unix_inflight++;
	spin_unlock(&unix_gc_lock);
}

void unix_notinflight(struct user_struct *user, struct file *fp)
{
	struct sock *s = unix_get_socket(fp);

	spin_lock(&unix_gc_lock);

	if (s) {
		struct unix_sock *u = unix_sk(s);

		BUG_ON(!atomic_long_read(&u->inflight));
		BUG_ON(list_empty(&u->link));

		if (atomic_long_dec_and_test(&u->inflight))
			list_del_init(&u->link);
		unix_tot_inflight--;
	}
	user->unix_inflight--;
	spin_unlock(&unix_gc_lock);
}

/*
 * The "user->unix_inflight" variable is protected by the garbage
 * collection lock, and we just read it locklessly here. If you go
 * over the limit, there might be a tiny race in actually noticing
 * it across threads. Tough.
 */
static inline bool too_many_unix_fds(struct task_struct *p)
{
	struct user_struct *user = current_user();

	if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
		return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
	return false;
}

int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
{
	int i;

	if (too_many_unix_fds(current))
		return -ETOOMANYREFS;

	/*
	 * Need to duplicate file references for the sake of garbage
	 * collection.  Otherwise a socket in the fps might become a
	 * candidate for GC while the skb is not yet queued.
	 */
	UNIXCB(skb).fp = scm_fp_dup(scm->fp);
	if (!UNIXCB(skb).fp)
		return -ENOMEM;

	for (i = scm->fp->count - 1; i >= 0; i--)
		unix_inflight(scm->fp->user, scm->fp->fp[i]);
	return 0;
}
EXPORT_SYMBOL(unix_attach_fds);

void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
{
	int i;

	scm->fp = UNIXCB(skb).fp;
	UNIXCB(skb).fp = NULL;

	for (i = scm->fp->count-1; i >= 0; i--)
		unix_notinflight(scm->fp->user, scm->fp->fp[i]);
}
EXPORT_SYMBOL(unix_detach_fds);

void unix_destruct_scm(struct sk_buff *skb)
{
	struct scm_cookie scm;

	memset(&scm, 0, sizeof(scm));
	scm.pid  = UNIXCB(skb).pid;
	if (UNIXCB(skb).fp)
		unix_detach_fds(&scm, skb);

	/* Alas, it calls VFS */
	/* So fscking what? fput() had been SMP-safe since the last Summer */
	scm_destroy(&scm);
	sock_wfree(skb);
}
EXPORT_SYMBOL(unix_destruct_scm);