io_uring/rsrc: disallow multi-source reg buffers

commit edd478269640b360c6f301f2baa04abdda563ef3 upstream.

If two or more mappings go back to back to each other they can be passed
into io_uring to be registered as a single registered buffer. That would
even work if mappings came from different sources, e.g. it's possible to
mix in this way anon pages and pages from shmem or hugetlb. That is not
a problem but it'd rather be less prone if we forbid such mixing.

Cc: <stable@vger.kernel.org>
Signed-off-by: Pavel Begunkov <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/rsrc.c b/io_uring/rsrc.c
index 55d4ab9..185d5df 100644 (file)
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1147,14 +1147,17 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages)
        pret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM,
                              pages, vmas);
        if (pret == nr_pages) {
+               struct file *file = vmas[0]->vm_file;
+
                /* don't support file backed memory */
                for (i = 0; i < nr_pages; i++) {
-                       struct vm_area_struct *vma = vmas[i];
-
-                       if (vma_is_shmem(vma))
+                       if (vmas[i]->vm_file != file) {
+                               ret = -EINVAL;
+                               break;
+                       }
+                       if (!file)
                                continue;
-                       if (vma->vm_file &&
-                           !is_file_hugepages(vma->vm_file)) {
+                       if (!vma_is_shmem(vmas[i]) && !is_file_hugepages(file)) {
                                ret = -EOPNOTSUPP;
                                break;
                        }