1 files changed, 151 insertions, 0 deletions

diff --git a/net/unix/scm.c b/net/unix/scm.c
new file mode 100644
index 000000000000..8c40f2b32392
--- /dev/null
+++ b/net/unix/scm.c
@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/socket.h>
+#include <linux/net.h>
+#include <linux/fs.h>
+#include <net/af_unix.h>
+#include <net/scm.h>
+#include <linux/init.h>
+
+#include "scm.h"
+
+unsigned int unix_tot_inflight;
+EXPORT_SYMBOL(unix_tot_inflight);
+
+LIST_HEAD(gc_inflight_list);
+EXPORT_SYMBOL(gc_inflight_list);
+
+DEFINE_SPINLOCK(unix_gc_lock);
+EXPORT_SYMBOL(unix_gc_lock);
+
+struct sock *unix_get_socket(struct file *filp)
+{
+        struct sock *u_sock = NULL;
+        struct inode *inode = file_inode(filp);
+
+        /* Socket ? */
+        if (S_ISSOCK(inode->i_mode) && !(filp->f_mode & FMODE_PATH)) {
+                struct socket *sock = SOCKET_I(inode);
+                struct sock *s = sock->sk;
+
+                /* PF_UNIX ? */
+                if (s && sock->ops && sock->ops->family == PF_UNIX)
+                        u_sock = s;
+        } else {
+                /* Could be an io_uring instance */
+                u_sock = io_uring_get_socket(filp);
+        }
+        return u_sock;
+}
+EXPORT_SYMBOL(unix_get_socket);
+
+/* Keep the number of times in flight count for the file
+ * descriptor if it is for an AF_UNIX socket.
+ */
+void unix_inflight(struct user_struct *user, struct file *fp)
+{
+        struct sock *s = unix_get_socket(fp);
+
+        spin_lock(&unix_gc_lock);
+
+        if (s) {
+                struct unix_sock *u = unix_sk(s);
+
+                if (atomic_long_inc_return(&u->inflight) == 1) {
+                        BUG_ON(!list_empty(&u->link));
+                        list_add_tail(&u->link, &gc_inflight_list);
+                } else {
+                        BUG_ON(list_empty(&u->link));
+                }
+                unix_tot_inflight++;
+        }
+        user->unix_inflight++;
+        spin_unlock(&unix_gc_lock);
+}
+
+void unix_notinflight(struct user_struct *user, struct file *fp)
+{
+        struct sock *s = unix_get_socket(fp);
+
+        spin_lock(&unix_gc_lock);
+
+        if (s) {
+                struct unix_sock *u = unix_sk(s);
+
+                BUG_ON(!atomic_long_read(&u->inflight));
+                BUG_ON(list_empty(&u->link));
+
+                if (atomic_long_dec_and_test(&u->inflight))
+                        list_del_init(&u->link);
+                unix_tot_inflight--;
+        }
+        user->unix_inflight--;
+        spin_unlock(&unix_gc_lock);
+}
+
+/*
+ * The "user->unix_inflight" variable is protected by the garbage
+ * collection lock, and we just read it locklessly here. If you go
+ * over the limit, there might be a tiny race in actually noticing
+ * it across threads. Tough.
+ */
+static inline bool too_many_unix_fds(struct task_struct *p)
+{
+        struct user_struct *user = current_user();
+
+        if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
+                return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
+        return false;
+}
+
+int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
+{
+        int i;
+
+        if (too_many_unix_fds(current))
+                return -ETOOMANYREFS;
+
+        /*
+         * Need to duplicate file references for the sake of garbage
+         * collection.  Otherwise a socket in the fps might become a
+         * candidate for GC while the skb is not yet queued.
+         */
+        UNIXCB(skb).fp = scm_fp_dup(scm->fp);
+        if (!UNIXCB(skb).fp)
+                return -ENOMEM;
+
+        for (i = scm->fp->count - 1; i >= 0; i--)
+                unix_inflight(scm->fp->user, scm->fp->fp[i]);
+        return 0;
+}
+EXPORT_SYMBOL(unix_attach_fds);
+
+void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
+{
+        int i;
+
+        scm->fp = UNIXCB(skb).fp;
+        UNIXCB(skb).fp = NULL;
+
+        for (i = scm->fp->count-1; i >= 0; i--)
+                unix_notinflight(scm->fp->user, scm->fp->fp[i]);
+}
+EXPORT_SYMBOL(unix_detach_fds);
+
+void unix_destruct_scm(struct sk_buff *skb)
+{
+        struct scm_cookie scm;
+
+        memset(&scm, 0, sizeof(scm));
+        scm.pid  = UNIXCB(skb).pid;
+        if (UNIXCB(skb).fp)
+                unix_detach_fds(&scm, skb);
+
+        /* Alas, it calls VFS */
+        /* So fscking what? fput() had been SMP-safe since the last Summer */
+        scm_destroy(&scm);
+        sock_wfree(skb);
+}
+EXPORT_SYMBOL(unix_destruct_scm);