Re: [syzbot] [mm?] WARNING in __folio_rmap_sanity_checks (2)

Hillf Danton
2024-12-30T11:17:34Z

On Fri, 27 Dec 2024 20:56:21 -0800
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 8155b4ef3466 Add linux-next specific files for 20241220
> git tree: linux-next
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1652fadf980000

#syz test

--- x/mm/filemap.c
+++ y/mm/filemap.c
@@ -3636,6 +3636,10 @@ static vm_fault_t filemap_map_folio_rang
continue;
skip:
if (count) {
+ for (unsigned int i = 0; i < count; i++) {
+ if (page_folio(page + i) != folio)
+ goto out;
+ }
set_pte_range(vmf, folio, page, count, addr);
*rss += count;
folio_ref_add(folio, count);
@@ -3658,6 +3662,7 @@ skip:
ret = VM_FAULT_NOPAGE;
}

+out:
vmf->pte = old_ptep;

return ret;
@@ -3738,8 +3743,8 @@ vm_fault_t filemap_map_pages(struct vm_f
addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
vmf->pte += xas.xa_index - last_pgoff;
last_pgoff = xas.xa_index;
- end = folio_next_index(folio) - 1;
- nr_pages = min(end, end_pgoff) - xas.xa_index + 1;
+ end = folio_next_index(folio);
+ nr_pages = min(end, end_pgoff) - xas.xa_index;

if (!folio_test_large(folio))
ret |= filemap_map_order0_folio(vmf,
--