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); 152