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>
8 #include <net/af_unix.h>
10 #include <linux/init.h>
14 unsigned int unix_tot_inflight;
15 EXPORT_SYMBOL(unix_tot_inflight);
17 LIST_HEAD(gc_inflight_list);
18 EXPORT_SYMBOL(gc_inflight_list);
20 DEFINE_SPINLOCK(unix_gc_lock);
21 EXPORT_SYMBOL(unix_gc_lock);
23 struct sock *unix_get_socket(struct file *filp)
25 struct sock *u_sock = NULL;
26 struct inode *inode = file_inode(filp);
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;
34 if (s && sock->ops && sock->ops->family == PF_UNIX)
37 /* Could be an io_uring instance */
38 u_sock = io_uring_get_socket(filp);
42 EXPORT_SYMBOL(unix_get_socket);
44 /* Keep the number of times in flight count for the file
45 * descriptor if it is for an AF_UNIX socket.
47 void unix_inflight(struct user_struct *user, struct file *fp)
49 struct sock *s = unix_get_socket(fp);
51 spin_lock(&unix_gc_lock);
54 struct unix_sock *u = unix_sk(s);
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);
60 BUG_ON(list_empty(&u->link));
62 /* Paired with READ_ONCE() in wait_for_unix_gc() */
63 WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
65 WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
66 spin_unlock(&unix_gc_lock);
69 void unix_notinflight(struct user_struct *user, struct file *fp)
71 struct sock *s = unix_get_socket(fp);
73 spin_lock(&unix_gc_lock);
76 struct unix_sock *u = unix_sk(s);
78 BUG_ON(!atomic_long_read(&u->inflight));
79 BUG_ON(list_empty(&u->link));
81 if (atomic_long_dec_and_test(&u->inflight))
82 list_del_init(&u->link);
83 /* Paired with READ_ONCE() in wait_for_unix_gc() */
84 WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
86 WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
87 spin_unlock(&unix_gc_lock);
91 * The "user->unix_inflight" variable is protected by the garbage
92 * collection lock, and we just read it locklessly here. If you go
93 * over the limit, there might be a tiny race in actually noticing
94 * it across threads. Tough.
96 static inline bool too_many_unix_fds(struct task_struct *p)
98 struct user_struct *user = current_user();
100 if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE)))
101 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
105 int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
109 if (too_many_unix_fds(current))
110 return -ETOOMANYREFS;
113 * Need to duplicate file references for the sake of garbage
114 * collection. Otherwise a socket in the fps might become a
115 * candidate for GC while the skb is not yet queued.
117 UNIXCB(skb).fp = scm_fp_dup(scm->fp);
121 for (i = scm->fp->count - 1; i >= 0; i--)
122 unix_inflight(scm->fp->user, scm->fp->fp[i]);
125 EXPORT_SYMBOL(unix_attach_fds);
127 void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
131 scm->fp = UNIXCB(skb).fp;
132 UNIXCB(skb).fp = NULL;
134 for (i = scm->fp->count-1; i >= 0; i--)
135 unix_notinflight(scm->fp->user, scm->fp->fp[i]);
137 EXPORT_SYMBOL(unix_detach_fds);
139 void unix_destruct_scm(struct sk_buff *skb)
141 struct scm_cookie scm;
143 memset(&scm, 0, sizeof(scm));
144 scm.pid = UNIXCB(skb).pid;
146 unix_detach_fds(&scm, skb);
148 /* Alas, it calls VFS */
149 /* So fscking what? fput() had been SMP-safe since the last Summer */
153 EXPORT_SYMBOL(unix_destruct_scm);