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 } 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 /* Paired with READ_ONCE() in wait_for_unix_gc() */ 63 WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1); 64 } 65 WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1); 66 spin_unlock(&unix_gc_lock); 67 } 68 69 void unix_notinflight(struct user_struct *user, struct file *fp) 70 { 71 struct sock *s = unix_get_socket(fp); 72 73 spin_lock(&unix_gc_lock); 74 75 if (s) { 76 struct unix_sock *u = unix_sk(s); 77 78 BUG_ON(!atomic_long_read(&u->inflight)); 79 BUG_ON(list_empty(&u->link)); 80 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); 85 } 86 WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1); 87 spin_unlock(&unix_gc_lock); 88 } 89 90 /* 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. 95 */ 96 static inline bool too_many_unix_fds(struct task_struct *p) 97 { 98 struct user_struct *user = current_user(); 99 100 if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE))) 101 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN); 102 return false; 103 } 104 105 int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb) 106 { 107 int i; 108 109 if (too_many_unix_fds(current)) 110 return -ETOOMANYREFS; 111 112 /* 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. 116 */ 117 UNIXCB(skb).fp = scm_fp_dup(scm->fp); 118 if (!UNIXCB(skb).fp) 119 return -ENOMEM; 120 121 for (i = scm->fp->count - 1; i >= 0; i--) 122 unix_inflight(scm->fp->user, scm->fp->fp[i]); 123 return 0; 124 } 125 EXPORT_SYMBOL(unix_attach_fds); 126 127 void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb) 128 { 129 int i; 130 131 scm->fp = UNIXCB(skb).fp; 132 UNIXCB(skb).fp = NULL; 133 134 for (i = scm->fp->count-1; i >= 0; i--) 135 unix_notinflight(scm->fp->user, scm->fp->fp[i]); 136 } 137 EXPORT_SYMBOL(unix_detach_fds); 138 139 void unix_destruct_scm(struct sk_buff *skb) 140 { 141 struct scm_cookie scm; 142 143 memset(&scm, 0, sizeof(scm)); 144 scm.pid = UNIXCB(skb).pid; 145 if (UNIXCB(skb).fp) 146 unix_detach_fds(&scm, skb); 147 148 /* Alas, it calls VFS */ 149 /* So fscking what? fput() had been SMP-safe since the last Summer */ 150 scm_destroy(&scm); 151 sock_wfree(skb); 152 } 153 EXPORT_SYMBOL(unix_destruct_scm); 154 155 void io_uring_destruct_scm(struct sk_buff *skb) 156 { 157 unix_destruct_scm(skb); 158 } 159 EXPORT_SYMBOL(io_uring_destruct_scm); 160