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