From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Subject: mm/filemap.c: remove bogus VM_BUG_ON It is not safe to check page->index without holding the page lock. It can be changed if the page is moved between the swap cache and the page cache for a shmem file, for example. There is a VM_BUG_ON below which checks page->index is correct after taking the page lock. Link: https://lkml.kernel.org/r/20210818144932.940640-1-willy@xxxxxxxxxxxxx Fixes: 5c211ba29deb ("mm: add and use find_lock_entries") Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Reported-by: <syzbot+c87be4f669d920c76330@xxxxxxxxxxxxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/filemap.c | 1 - 1 file changed, 1 deletion(-) --- a/mm/filemap.c~mm-remove-bogus-vm_bug_on +++ a/mm/filemap.c @@ -2093,7 +2093,6 @@ unsigned find_lock_entries(struct addres if (!xa_is_value(page)) { if (page->index < start) goto put; - VM_BUG_ON_PAGE(page->index != xas.xa_index, page); if (page->index + thp_nr_pages(page) - 1 > end) goto put; if (!trylock_page(page)) _
