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