net: remove sock_iocb

The sock_iocb structure is allocate on stack for each read/write-like
operation on sockets, and contains various fields of which only the
embedded msghdr and sometimes a pointer to the scm_cookie is ever used.
Get rid of the sock_iocb and put a msghdr directly on the stack and pass
the scm_cookie explicitly to netlink_mmap_sendmsg.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 44 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 8e1b10274b02..526b6edab018 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1445,7 +1445,6 @@ static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
 static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
                               struct msghdr *msg, size_t len)
 {
-        struct sock_iocb *siocb = kiocb_to_siocb(kiocb);
         struct sock *sk = sock->sk;
         struct net *net = sock_net(sk);
         struct unix_sock *u = unix_sk(sk);
@@ -1456,14 +1455,12 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
         unsigned int hash;
         struct sk_buff *skb;
         long timeo;
-        struct scm_cookie tmp_scm;
+        struct scm_cookie scm;
         int max_level;
         int data_len = 0;
 
-        if (NULL == siocb->scm)
-                siocb->scm = &tmp_scm;
         wait_for_unix_gc();
-        err = scm_send(sock, msg, siocb->scm, false);
+        err = scm_send(sock, msg, &scm, false);
         if (err < 0)
                 return err;
 
@@ -1507,11 +1504,11 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
         if (skb == NULL)
                 goto out;
 
-        err = unix_scm_to_skb(siocb->scm, skb, true);
+        err = unix_scm_to_skb(&scm, skb, true);
         if (err < 0)
                 goto out_free;
         max_level = err + 1;
-        unix_get_secdata(siocb->scm, skb);
+        unix_get_secdata(&scm, skb);
 
         skb_put(skb, len - data_len);
         skb->data_len = data_len;
@@ -1606,7 +1603,7 @@ restart:
         unix_state_unlock(other);
         other->sk_data_ready(other);
         sock_put(other);
-        scm_destroy(siocb->scm);
+        scm_destroy(&scm);
         return len;
 
 out_unlock:
@@ -1616,7 +1613,7 @@ out_free:
 out:
         if (other)
                 sock_put(other);
-        scm_destroy(siocb->scm);
+        scm_destroy(&scm);
         return err;
 }
 
@@ -1628,21 +1625,18 @@ out:
 static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                                struct msghdr *msg, size_t len)
 {
-        struct sock_iocb *siocb = kiocb_to_siocb(kiocb);
         struct sock *sk = sock->sk;
         struct sock *other = NULL;
         int err, size;
         struct sk_buff *skb;
         int sent = 0;
-        struct scm_cookie tmp_scm;
+        struct scm_cookie scm;
         bool fds_sent = false;
         int max_level;
         int data_len;
 
-        if (NULL == siocb->scm)
-                siocb->scm = &tmp_scm;
         wait_for_unix_gc();
-        err = scm_send(sock, msg, siocb->scm, false);
+        err = scm_send(sock, msg, &scm, false);
         if (err < 0)
                 return err;
 
@@ -1683,7 +1677,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                         goto out_err;
 
                 /* Only send the fds in the first buffer */
-                err = unix_scm_to_skb(siocb->scm, skb, !fds_sent);
+                err = unix_scm_to_skb(&scm, skb, !fds_sent);
                 if (err < 0) {
                         kfree_skb(skb);
                         goto out_err;
@@ -1715,8 +1709,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                 sent += size;
         }
 
-        scm_destroy(siocb->scm);
-        siocb->scm = NULL;
+        scm_destroy(&scm);
 
         return sent;
 
@@ -1728,8 +1721,7 @@ pipe_err:
                 send_sig(SIGPIPE, current, 0);
         err = -EPIPE;
 out_err:
-        scm_destroy(siocb->scm);
-        siocb->scm = NULL;
+        scm_destroy(&scm);
         return sent ? : err;
 }
 
@@ -1778,8 +1770,7 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
                               struct msghdr *msg, size_t size,
                               int flags)
 {
-        struct sock_iocb *siocb = kiocb_to_siocb(iocb);
-        struct scm_cookie tmp_scm;
+        struct scm_cookie scm;
         struct sock *sk = sock->sk;
         struct unix_sock *u = unix_sk(sk);
         int noblock = flags & MSG_DONTWAIT;
@@ -1831,16 +1822,14 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
         if (sock_flag(sk, SOCK_RCVTSTAMP))
                 __sock_recv_timestamp(msg, sk, skb);
 
-        if (!siocb->scm) {
-                siocb->scm = &tmp_scm;
-                memset(&tmp_scm, 0, sizeof(tmp_scm));
-        }
-        scm_set_cred(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
-        unix_set_secdata(siocb->scm, skb);
+        memset(&scm, 0, sizeof(scm));
+
+        scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
+        unix_set_secdata(&scm, skb);
 
         if (!(flags & MSG_PEEK)) {
                 if (UNIXCB(skb).fp)
-                        unix_detach_fds(siocb->scm, skb);
+                        unix_detach_fds(&scm, skb);
 
                 sk_peek_offset_bwd(sk, skb->len);
         } else {
@@ -1860,11 +1849,11 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
                 sk_peek_offset_fwd(sk, size);
 
                 if (UNIXCB(skb).fp)
-                        siocb->scm->fp = scm_fp_dup(UNIXCB(skb).fp);
+                        scm.fp = scm_fp_dup(UNIXCB(skb).fp);
         }
         err = (flags & MSG_TRUNC) ? skb->len - skip : size;
 
-        scm_recv(sock, msg, siocb->scm, flags);
+        scm_recv(sock, msg, &scm, flags);
 
 out_free:
         skb_free_datagram(sk, skb);
@@ -1915,8 +1904,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
                                struct msghdr *msg, size_t size,
                                int flags)
 {
-        struct sock_iocb *siocb = kiocb_to_siocb(iocb);
-        struct scm_cookie tmp_scm;
+        struct scm_cookie scm;
         struct sock *sk = sock->sk;
         struct unix_sock *u = unix_sk(sk);
         DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr, msg->msg_name);
@@ -1943,10 +1931,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
          * while sleeps in memcpy_tomsg
          */
 
-        if (!siocb->scm) {
-                siocb->scm = &tmp_scm;
-                memset(&tmp_scm, 0, sizeof(tmp_scm));
-        }
+        memset(&scm, 0, sizeof(scm));
 
         err = mutex_lock_interruptible(&u->readlock);
         if (unlikely(err)) {
@@ -2012,13 +1997,13 @@ again:
 
                 if (check_creds) {
                         /* Never glue messages from different writers */
-                        if ((UNIXCB(skb).pid  != siocb->scm->pid) ||
-                            !uid_eq(UNIXCB(skb).uid, siocb->scm->creds.uid) ||
-                            !gid_eq(UNIXCB(skb).gid, siocb->scm->creds.gid))
+                        if ((UNIXCB(skb).pid  != scm.pid) ||
+                            !uid_eq(UNIXCB(skb).uid, scm.creds.uid) ||
+                            !gid_eq(UNIXCB(skb).gid, scm.creds.gid))
                                 break;
                 } else if (test_bit(SOCK_PASSCRED, &sock->flags)) {
                         /* Copy credentials */
-                        scm_set_cred(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
+                        scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
                         check_creds = 1;
                 }
 
@@ -2045,7 +2030,7 @@ again:
                         sk_peek_offset_bwd(sk, chunk);
 
                         if (UNIXCB(skb).fp)
-                                unix_detach_fds(siocb->scm, skb);
+                                unix_detach_fds(&scm, skb);
 
                         if (unix_skb_len(skb))
                                 break;
@@ -2053,13 +2038,13 @@ again:
                         skb_unlink(skb, &sk->sk_receive_queue);
                         consume_skb(skb);
 
-                        if (siocb->scm->fp)
+                        if (scm.fp)
                                 break;
                 } else {
                         /* It is questionable, see note in unix_dgram_recvmsg.
                          */
                         if (UNIXCB(skb).fp)
-                                siocb->scm->fp = scm_fp_dup(UNIXCB(skb).fp);
+                                scm.fp = scm_fp_dup(UNIXCB(skb).fp);
 
                         sk_peek_offset_fwd(sk, chunk);
 
@@ -2068,7 +2053,7 @@ again:
         } while (size);
 
         mutex_unlock(&u->readlock);
-        scm_recv(sock, msg, siocb->scm, flags);
+        scm_recv(sock, msg, &scm, flags);
 out:
         return copied ? : err;
 }