socketpair(): allocate descriptors first

simplifies failure exits considerably...

Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 38 insertions, 51 deletions

diff --git a/net/socket.c b/net/socket.c
index 42d8e9c9ccd5..2df83c0bfde9 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1366,87 +1366,74 @@ SYSCALL_DEFINE4(socketpair, int, family, int, type, int, protocol,
                 flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
 
         /*
+         * reserve descriptors and make sure we won't fail
+         * to return them to userland.
+         */
+        fd1 = get_unused_fd_flags(flags);
+        if (unlikely(fd1 < 0))
+                return fd1;
+
+        fd2 = get_unused_fd_flags(flags);
+        if (unlikely(fd2 < 0)) {
+                put_unused_fd(fd1);
+                return fd2;
+        }
+
+        err = put_user(fd1, &usockvec[0]);
+        if (err)
+                goto out;
+
+        err = put_user(fd2, &usockvec[1]);
+        if (err)
+                goto out;
+
+        /*
          * Obtain the first socket and check if the underlying protocol
          * supports the socketpair call.
          */
 
         err = sock_create(family, type, protocol, &sock1);
-        if (err < 0)
+        if (unlikely(err < 0))
                 goto out;
 
         err = sock_create(family, type, protocol, &sock2);
-        if (err < 0)
-                goto out_release_1;
-
-        err = sock1->ops->socketpair(sock1, sock2);
-        if (err < 0)
-                goto out_release_both;
-
-        fd1 = get_unused_fd_flags(flags);
-        if (unlikely(fd1 < 0)) {
-                err = fd1;
-                goto out_release_both;
+        if (unlikely(err < 0)) {
+                sock_release(sock1);
+                goto out;
         }
 
-        fd2 = get_unused_fd_flags(flags);
-        if (unlikely(fd2 < 0)) {
-                err = fd2;
-                goto out_put_unused_1;
+        err = sock1->ops->socketpair(sock1, sock2);
+        if (unlikely(err < 0)) {
+                sock_release(sock2);
+                sock_release(sock1);
+                goto out;
         }
 
         newfile1 = sock_alloc_file(sock1, flags, NULL);
         if (IS_ERR(newfile1)) {
                 err = PTR_ERR(newfile1);
-                goto out_put_unused_both;
+                sock_release(sock1);
+                sock_release(sock2);
+                goto out;
         }
 
         newfile2 = sock_alloc_file(sock2, flags, NULL);
         if (IS_ERR(newfile2)) {
                 err = PTR_ERR(newfile2);
-                goto out_fput_1;
+                sock_release(sock2);
+                fput(newfile1);
+                goto out;
         }
 
-        err = put_user(fd1, &usockvec[0]);
-        if (err)
-                goto out_fput_both;
-
-        err = put_user(fd2, &usockvec[1]);
-        if (err)
-                goto out_fput_both;
-
         audit_fd_pair(fd1, fd2);
 
         fd_install(fd1, newfile1);
         fd_install(fd2, newfile2);
-        /* fd1 and fd2 may be already another descriptors.
-         * Not kernel problem.
-         */
-
         return 0;
 
-out_fput_both:
-        fput(newfile2);
-        fput(newfile1);
-        put_unused_fd(fd2);
-        put_unused_fd(fd1);
-        goto out;
-
-out_fput_1:
-        fput(newfile1);
-        put_unused_fd(fd2);
-        put_unused_fd(fd1);
-        sock_release(sock2);
-        goto out;
-
-out_put_unused_both:
+out:
         put_unused_fd(fd2);
-out_put_unused_1:
         put_unused_fd(fd1);
-out_release_both:
-        sock_release(sock2);
-out_release_1:
-        sock_release(sock1);
-out:
         return err;
 }