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 15 unsigned int unix_tot_inflight; 16 EXPORT_SYMBOL(unix_tot_inflight); 17 18 LIST_HEAD(gc_inflight_list); 19 EXPORT_SYMBOL(gc_inflight_list); 20 21 DEFINE_SPINLOCK(unix_gc_lock); 22 EXPORT_SYMBOL(unix_gc_lock); 23 24 struct 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 const struct proto_ops *ops = READ_ONCE(sock->ops); 33 struct sock *s = sock->sk; 34 35 /* PF_UNIX ? */ 36 if (s && ops && ops->family == PF_UNIX) 37 u_sock = s; 38 } else { 39 /* Could be an io_uring instance */ 40 u_sock = io_uring_get_socket(filp); 41 } 42 return u_sock; 43 } 44 EXPORT_SYMBOL(unix_get_socket); 45 46 /* Keep the number of times in flight count for the file 47 * descriptor if it is for an AF_UNIX socket. 48 */ 49 void unix_inflight(struct user_struct *user, struct file *fp) 50 { 51 struct sock *s = unix_get_socket(fp); 52 53 spin_lock(&unix_gc_lock); 54 55 if (s) { 56 struct unix_sock *u = unix_sk(s); 57 58 if (atomic_long_inc_return(&u->inflight) == 1) { 59 BUG_ON(!list_empty(&u->link)); 60 list_add_tail(&u->link, &gc_inflight_list); 61 } else { 62 BUG_ON(list_empty(&u->link)); 63 } 64 /* Paired with READ_ONCE() in wait_for_unix_gc() */ 65 WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1); 66 } 67 WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1); 68 spin_unlock(&unix_gc_lock); 69 } 70 71 void unix_notinflight(struct user_struct *user, struct file *fp) 72 { 73 struct sock *s = unix_get_socket(fp); 74 75 spin_lock(&unix_gc_lock); 76 77 if (s) { 78 struct unix_sock *u = unix_sk(s); 79 80 BUG_ON(!atomic_long_read(&u->inflight)); 81 BUG_ON(list_empty(&u->link)); 82 83 if (atomic_long_dec_and_test(&u->inflight)) 84 list_del_init(&u->link); 85 /* Paired with READ_ONCE() in wait_for_unix_gc() */ 86 WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1); 87 } 88 WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1); 89 spin_unlock(&unix_gc_lock); 90 } 91 92 /* 93 * The "user->unix_inflight" variable is protected by the garbage 94 * collection lock, and we just read it locklessly here. If you go 95 * over the limit, there might be a tiny race in actually noticing 96 * it across threads. Tough. 97 */ 98 static inline bool too_many_unix_fds(struct task_struct *p) 99 { 100 struct user_struct *user = current_user(); 101 102 if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE))) 103 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN); 104 return false; 105 } 106 107 int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb) 108 { 109 int i; 110 111 if (too_many_unix_fds(current)) 112 return -ETOOMANYREFS; 113 114 /* 115 * Need to duplicate file references for the sake of garbage 116 * collection. Otherwise a socket in the fps might become a 117 * candidate for GC while the skb is not yet queued. 118 */ 119 UNIXCB(skb).fp = scm_fp_dup(scm->fp); 120 if (!UNIXCB(skb).fp) 121 return -ENOMEM; 122 123 for (i = scm->fp->count - 1; i >= 0; i--) 124 unix_inflight(scm->fp->user, scm->fp->fp[i]); 125 return 0; 126 } 127 EXPORT_SYMBOL(unix_attach_fds); 128 129 void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb) 130 { 131 int i; 132 133 scm->fp = UNIXCB(skb).fp; 134 UNIXCB(skb).fp = NULL; 135 136 for (i = scm->fp->count-1; i >= 0; i--) 137 unix_notinflight(scm->fp->user, scm->fp->fp[i]); 138 } 139 EXPORT_SYMBOL(unix_detach_fds); 140 141 void unix_destruct_scm(struct sk_buff *skb) 142 { 143 struct scm_cookie scm; 144 145 memset(&scm, 0, sizeof(scm)); 146 scm.pid = UNIXCB(skb).pid; 147 if (UNIXCB(skb).fp) 148 unix_detach_fds(&scm, skb); 149 150 /* Alas, it calls VFS */ 151 /* So fscking what? fput() had been SMP-safe since the last Summer */ 152 scm_destroy(&scm); 153 sock_wfree(skb); 154 } 155 EXPORT_SYMBOL(unix_destruct_scm); 156 157 void io_uring_destruct_scm(struct sk_buff *skb) 158 { 159 unix_destruct_scm(skb); 160 } 161 EXPORT_SYMBOL(io_uring_destruct_scm); 162