linux-kernel - [PATCH AUTOSEL 4.4 72/80] mm/page_owner: clamp read count to PAGE

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Message-Id: <20190128162401.58841-72-sashal@kernel.org>
Date:   Mon, 28 Jan 2019 11:23:53 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Miles Chen <miles.chen@...iatek.com>,
        Joe Perches <joe@...ches.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-mm@...ck.org
Subject: [PATCH AUTOSEL 4.4 72/80] mm/page_owner: clamp read count to PAGE_SIZE

From: Miles Chen <miles.chen@...iatek.com>

[ 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@...ux-foundation.org: use min_t()]
Link: http://lkml.kernel.org/r/1541091607-27402-1-git-send-email-miles.chen@mediatek.com
Signed-off-by: Miles Chen <miles.chen@...iatek.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Cc: Joe Perches <joe@...ches.com>
Cc: Matthew Wilcox <willy@...radead.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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