io_uring/af_unix: disable sending io_uring over sockets

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>

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 8625181fb87acfc81c1dd56ff043c1baa399a92a..08ac0d8e07ef84e8138579a0b7c6436a9bc7e425 100644 (file)
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -77,17 +77,10 @@ int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
 
 int __io_scm_file_account(struct io_ring_ctx *ctx, struct file *file);
 
-#if defined(CONFIG_UNIX)
-static inline bool io_file_need_scm(struct file *filp)
-{
-       return !!unix_get_socket(filp);
-}
-#else
 static inline bool io_file_need_scm(struct file *filp)
 {
        return false;
 }
-#endif
 
 static inline int io_scm_file_account(struct io_ring_ctx *ctx,
                                      struct file *file)

diff --git a/net/core/scm.c b/net/core/scm.c
index 880027ecf516503c6b98d1190aabca3c3be24e99..7dc47c17d8638a79960cee0a4cc8fd3fedd624fe 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++;
        }