[PATCH AUTOSEL 4.4 72/80] mm/page_owner: clamp read count to PAGE_SIZE

[Sasha Levin]

From: Miles Chen <miles.chen@xxxxxxxxxxxx>

[ Upstream commit c8f61cfc871fadfb73ad3eacd64fda457279e911 ]

The (root-only) page owner read might allocate a large size of memory with
a large read count.  Allocation fails can easily occur when doing high
order allocations.

Clamp buffer size to PAGE_SIZE to avoid arbitrary size allocation
and avoid allocation fails due to high order allocation.

[akpm@xxxxxxxxxxxxxxxxxxxx: use min_t()]
Link: http://lkml.kernel.org/r/1541091607-27402-1-git-send-email-miles.chen@xxxxxxxxxxxx
Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/page_owner.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index dd6b9cebf981..9c9f32fa70fa 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -107,6 +107,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 		.entries = &page_ext->trace_entries[0],
 	};
 
+	count = min_t(size_t, count, PAGE_SIZE);
 	kbuf = kmalloc(count, GFP_KERNEL);
 	if (!kbuf)
 		return -ENOMEM;
-- 
2.19.1