9p: pass the correct prototype to read_cache_page

[ Upstream commit f053cbd4366051d7eb6ba1b8d529d20f719c2963 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 6181ad7..e45b1a0 100644 (file)
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -49,8 +49,9 @@
  * @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;
@@ -121,7 +122,8 @@ 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;
 }