9p: pass the correct prototype to read_cache_page

Fix the callback 9p passes to read_cache_page to actually have the
proper type expected.  Casting around function pointers can easily
hide typing bugs, and defeats control flow protection.

Link: http://lkml.kernel.org/r/20190520055731.24538-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index bc57ae9e2963..cce9ace651a2 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -35,8 +35,9 @@
  * @page: structure to page
  *
  */
-static int v9fs_fid_readpage(struct p9_fid *fid, struct page *page)
+static int v9fs_fid_readpage(void *data, struct page *page)
 {
+        struct p9_fid *fid = data;
         struct inode *inode = page->mapping->host;
         struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
         struct iov_iter to;
@@ -107,7 +108,8 @@ static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
         if (ret == 0)
                 return ret;
 
-        ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp);
+        ret = read_cache_pages(mapping, pages, v9fs_fid_readpage,
+                        filp->private_data);
         p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
         return ret;
 }