io_uring/af_unix: disable sending io_uring over sockets

commit 705318a99a138c29a512a72c3e0043b3cd7f55f4 upstream.

File reference cycles have caused lots of problems for io_uring
in the past, and it still doesn't work exactly right and races with
unix_stream_read_generic(). The safest fix would be to completely
disallow sending io_uring files via sockets via SCM_RIGHT, so there
are no possible cycles invloving registered files and thus rendering
SCM accounting on the io_uring side unnecessary.

Cc:  <stable@vger.kernel.org>
Fixes: 0091bfc81741b ("io_uring/af_unix: defer registered files gc to io_uring release")
Reported-and-suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c716c88321939156909cfa1bd8b0faaf1c804103.1701868795.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 95e7ce84fa2ac13718e1c4317d6562331440e48b..30535d4edee7529da865c942234d83458411e4ce 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -8627,49 +8627,6 @@ out_free:
        return ret;
 }
 
-static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
-                               int index)
-{
-#if defined(CONFIG_UNIX)
-       struct sock *sock = ctx->ring_sock->sk;
-       struct sk_buff_head *head = &sock->sk_receive_queue;
-       struct sk_buff *skb;
-
-       /*
-        * See if we can merge this file into an existing skb SCM_RIGHTS
-        * file set. If there's no room, fall back to allocating a new skb
-        * and filling it in.
-        */
-       spin_lock_irq(&head->lock);
-       skb = skb_peek(head);
-       if (skb) {
-               struct scm_fp_list *fpl = UNIXCB(skb).fp;
-
-               if (fpl->count < SCM_MAX_FD) {
-                       __skb_unlink(skb, head);
-                       spin_unlock_irq(&head->lock);
-                       fpl->fp[fpl->count] = get_file(file);
-                       unix_inflight(fpl->user, fpl->fp[fpl->count]);
-                       fpl->count++;
-                       spin_lock_irq(&head->lock);
-                       __skb_queue_head(head, skb);
-               } else {
-                       skb = NULL;
-               }
-       }
-       spin_unlock_irq(&head->lock);
-
-       if (skb) {
-               fput(file);
-               return 0;
-       }
-
-       return __io_sqe_files_scm(ctx, 1, index);
-#else
-       return 0;
-#endif
-}
-
 static int io_queue_rsrc_removal(struct io_rsrc_data *data, unsigned idx,
                                 struct io_rsrc_node *node, void *rsrc)
 {
@@ -8727,12 +8684,6 @@ static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
 
        *io_get_tag_slot(ctx->file_data, slot_index) = 0;
        io_fixed_file_set(file_slot, file);
-       ret = io_sqe_file_register(ctx, file, slot_index);
-       if (ret) {
-               file_slot->file_ptr = 0;
-               goto err;
-       }
-
        ret = 0;
 err:
        if (needs_switch)
@@ -8846,12 +8797,6 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                        }
                        *io_get_tag_slot(data, i) = tag;
                        io_fixed_file_set(file_slot, file);
-                       err = io_sqe_file_register(ctx, file, i);
-                       if (err) {
-                               file_slot->file_ptr = 0;
-                               fput(file);
-                               break;
-                       }
                }
        }
 

diff --git a/net/core/scm.c b/net/core/scm.c
index acb7d776fa6ec29cdd9ae7d3a9970384c887ac75..e762a4b8a1d220e05afd4de364cc421fda776b5d 100644 (file)
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -26,6 +26,7 @@
 #include <linux/nsproxy.h>
 #include <linux/slab.h>
 #include <linux/errqueue.h>
+#include <linux/io_uring.h>
 
 #include <linux/uaccess.h>
 
@@ -103,6 +104,11 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
 
                if (fd < 0 || !(file = fget_raw(fd)))
                        return -EBADF;
+               /* don't allow io_uring files */
+               if (io_uring_get_socket(file)) {
+                       fput(file);
+                       return -EINVAL;
+               }
                *fpp++ = file;
                fpl->count++;
        }