From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: 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: dd6bd0d9c7db ("swap: use bdev_read_page() / bdev_write_page()")
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff -puN mm/filemap.c~mm-do-not-access-page-mapping-directly-on-page_endio mm/filemap.c
--- a/mm/filemap.c~mm-do-not-access-page-mapping-directly-on-page_endio
+++ a/mm/filemap.c
@@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool
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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