fuse: prevent folio use-after-free in readahead

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cherry-picked-for: https://gitlab.archlinux.org/archlinux/packaging/packages/linux/-/issues/110

fs/fuse/file.c

@@ -955,8 +955,10 @@ static void fuse_readpages_end(struct fuse_mount *fm, struct fuse_args *args,
 		fuse_invalidate_atime(inode);
 	}
 
-	for (i = 0; i < ap->num_folios; i++)
+	for (i = 0; i < ap->num_folios; i++) {
 		folio_end_read(ap->folios[i], !err);
+		folio_put(ap->folios[i]);
+	}
 	if (ia->ff)
 		fuse_file_put(ia->ff, false);
 
@@ -1048,7 +1050,7 @@ static void fuse_readahead(struct readahead_control *rac)
 		ap = &ia->ap;
 
 		while (ap->num_folios < cur_pages) {
-			folio = readahead_folio(rac);
+			folio = __readahead_folio(rac);
 			ap->folios[ap->num_folios] = folio;
 			ap->descs[ap->num_folios].length = folio_size(folio);
 			ap->num_folios++;