[PATCH 3.18 07/24] mm/filemap.c: fix NULL pointer in page_cache_tree_insert()

From: Greg Kroah-Hartman
Date: Fri Apr 27 2018 - 10:00:41 EST

3.18-stable review patch. If anyone has any objections, please let me know.


From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>

commit abc1be13fd113ddef5e2d807a466286b864caed3 upstream.

f2fs specifies the __GFP_ZERO flag for allocating some of its pages.
Unfortunately, the page cache also uses the mapping's GFP flags for
allocating radix tree nodes. It always masked off the __GFP_HIGHMEM
flag, and masks off __GFP_ZERO in some paths, but not all. That causes
radix tree nodes to be allocated with a NULL list_head, which causes
backtraces like:


The __GFP_DMA and __GFP_DMA32 flags would also be able to sneak through
if they are ever used. Fix them all by using GFP_RECLAIM_MASK at the
innermost location, and remove it from earlier in the callchain.

Link: http://lkml.kernel.org/r/20180411060320.14458-2-willy@xxxxxxxxxxxxx
Fixes: 449dd6984d0e ("mm: keep page cache radix tree nodes in check")
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Reported-by: Chris Fries <cfries@xxxxxxxxxx>
Debugged-by: Minchan Kim <minchan@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Harsh Shandilya <harsh@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
mm/filemap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -468,7 +468,7 @@ int replace_page_cache_page(struct page
VM_BUG_ON_PAGE(!PageLocked(new), new);
VM_BUG_ON_PAGE(new->mapping, new);

- error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
+ error = radix_tree_preload(gfp_mask & GFP_RECLAIM_MASK);
if (!error) {
struct address_space *mapping = old->mapping;
void (*freepage)(struct page *);
@@ -561,7 +561,7 @@ static int __add_to_page_cache_locked(st
return error;

- error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
+ error = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK);
if (error) {
if (!huge)
mem_cgroup_cancel_charge(page, memcg);