Commit dd8416c4 authored Feb 24, 2017 by Minchan Kim Committed by Linus Torvalds Feb 24, 2017

mm: do not access page->mapping directly on page_endio



With rw_page, page_endio is used for completing IO on a page and it
propagates write error to the address space if the IO fails.  The
problem is it accesses page->mapping directly which might be okay for
file-backed pages but it shouldn't for anonymous page.  Otherwise, it
can corrupt one of field from anon_vma under us and system goes panic
randomly.

swap_writepage
  bdev_writepage
    ops->rw_page

I encountered the BUG during developing new zram feature and it was
really hard to figure it out because it made random crash, somtime
mmap_sem lockdep, sometime other places where places never related to
zram/zsmalloc, and not reproducible with some configuration.

When I consider how that bug is subtle and people do fast-swap test with
brd, it's worth to add stable mark, I think.

Fixes: dd6bd0d9 ("swap: use bdev_read_page() / bdev_write_page()")
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 9a8b300f

mm/filemap.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int err)
		unlock_page(page);
		} else {
		if (err) {
		struct address_space *mapping;

		SetPageError(page);
		if (page->mapping)
		mapping_set_error(page->mapping, err);
		mapping = page_mapping(page);
		if (mapping)
		mapping_set_error(mapping, err);
		}
		end_page_writeback(page);
		}

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