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 /* Paired with READ_ONCE() in wait_for_unix_gc() */ 64 WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1); 65 } 66 user->unix_inflight++; 67 spin_unlock(&unix_gc_lock); 68 } 69 70 void unix_notinflight(struct user_struct *user, struct file *fp) 71 { 72 struct sock *s = unix_get_socket(fp); 73 74 spin_lock(&unix_gc_lock); 75 76 if (s) { 77 struct unix_sock *u = unix_sk(s); 78 79 BUG_ON(!atomic_long_read(&u->inflight)); 80 BUG_ON(list_empty(&u->link)); 81 82 if (atomic_long_dec_and_test(&u->inflight)) 83 list_del_init(&u->link); 84 /* Paired with READ_ONCE() in wait_for_unix_gc() */ 85 WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1); 86 } 87 user->unix_inflight--; 88 spin_unlock(&unix_gc_lock); 89 } 90 91 /* 92 * The "user->unix_inflight" variable is protected by the garbage 93 * collection lock, and we just read it locklessly here. If you go 94 * over the limit, there might be a tiny race in actually noticing 95 * it across threads. Tough. 96 */ 97 static inline bool too_many_unix_fds(struct task_struct *p) 98 { 99 struct user_struct *user = current_user(); 100 101 if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE))) 102 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN); 103 return false; 104 } 105 106 int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb) 107 { 108 int i; 109 110 if (too_many_unix_fds(current)) 111 return -ETOOMANYREFS; 112 113 /* 114 * Need to duplicate file references for the sake of garbage 115 * collection. Otherwise a socket in the fps might become a 116 * candidate for GC while the skb is not yet queued. 117 */ 118 UNIXCB(skb).fp = scm_fp_dup(scm->fp); 119 if (!UNIXCB(skb).fp) 120 return -ENOMEM; 121 122 for (i = scm->fp->count - 1; i >= 0; i--) 123 unix_inflight(scm->fp->user, scm->fp->fp[i]); 124 return 0; 125 } 126 EXPORT_SYMBOL(unix_attach_fds); 127 128 void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb) 129 { 130 int i; 131 132 scm->fp = UNIXCB(skb).fp; 133 UNIXCB(skb).fp = NULL; 134 135 for (i = scm->fp->count-1; i >= 0; i--) 136 unix_notinflight(scm->fp->user, scm->fp->fp[i]); 137 } 138 EXPORT_SYMBOL(unix_detach_fds); 139 140 void unix_destruct_scm(struct sk_buff *skb) 141 { 142 struct scm_cookie scm; 143 144 memset(&scm, 0, sizeof(scm)); 145 scm.pid = UNIXCB(skb).pid; 146 if (UNIXCB(skb).fp) 147 unix_detach_fds(&scm, skb); 148 149 /* Alas, it calls VFS */ 150 /* So fscking what? fput() had been SMP-safe since the last Summer */ 151 scm_destroy(&scm); 152 sock_wfree(skb); 153 } 154 EXPORT_SYMBOL(unix_destruct_scm); 155 156 void io_uring_destruct_scm(struct sk_buff *skb) 157 { 158 unix_destruct_scm(skb); 159 } 160 EXPORT_SYMBOL(io_uring_destruct_scm); 161