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[198.145.29.99]) by mx.google.com with ESMTPS id k11si134196pll.377.2019.07.18.21.01.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 21:01:59 -0700 (PDT) Received-SPF: pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=tG6QkiUH; spf=pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sashal@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 014FA21851; Fri, 19 Jul 2019 04:01:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563508919; bh=hd3faQ3NjDa7987x5ieUJyMgS5PrMg+h5OFV8vUuDas=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tG6QkiUH0qtVSPFmuzV7qsEUFaGrl9xhD6GIffsJTLPEiJo/dKYvARlAqWE8J/su1 puKv24BAxPl5r3ThTtsFUr01x4SqaCXGa9b06pjsC16JjQ4nMP+ErLVToAtM5UlG6Q 4Sndwi6lUKKP7xxRd0qJ4ktgtqnzh5rVzpWzbep8= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Huang Ying , Andrew Morton , Michal Hocko , Hugh Dickins , "Paul E . McKenney" , Minchan Kim , Johannes Weiner , Tim Chen , Mel Gorman , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Andrea Arcangeli , Yang Shi , David Rientjes , Rik van Riel , Jan Kara , Dave Jiang , Daniel Jordan , Andrea Parri , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 5.2 158/171] mm/mincore.c: fix race between swapoff and mincore Date: Thu, 18 Jul 2019 23:56:29 -0400 Message-Id: <20190719035643.14300-158-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190719035643.14300-1-sashal@kernel.org> References: <20190719035643.14300-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Huang Ying [ Upstream commit aeb309b81c6bada783c3695528a3e10748e97285 ] Via commit 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks"), after swapoff, the address_space associated with the swap device will be freed. So swap_address_space() users which touch the address_space need some kind of mechanism to prevent the address_space from being freed during accessing. When mincore processes an unmapped range for swapped shmem pages, it doesn't hold the lock to prevent swap device from being swapped off. So the following race is possible: CPU1 CPU2 do_mincore() swapoff() walk_page_range() mincore_unmapped_range() __mincore_unmapped_range mincore_page as = swap_address_space() ... exit_swap_address_space() ... kvfree(spaces) find_get_page(as) The address space may be accessed after being freed. To fix the race, get_swap_device()/put_swap_device() is used to enclose find_get_page() to check whether the swap entry is valid and prevent the swap device from being swapoff during accessing. Link: http://lkml.kernel.org/r/20190611020510.28251-1-ying.huang@intel.com Fixes: 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks") Signed-off-by: "Huang, Ying" Reviewed-by: Andrew Morton Acked-by: Michal Hocko Cc: Hugh Dickins Cc: Paul E. McKenney Cc: Minchan Kim Cc: Johannes Weiner Cc: Tim Chen Cc: Mel Gorman Cc: Jérôme Glisse Cc: Andrea Arcangeli Cc: Yang Shi Cc: David Rientjes Cc: Rik van Riel Cc: Jan Kara Cc: Dave Jiang Cc: Daniel Jordan Cc: Andrea Parri Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/mincore.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/mincore.c b/mm/mincore.c index c3f058bd0faf..4fe91d497436 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -68,8 +68,16 @@ static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) */ if (xa_is_value(page)) { swp_entry_t swp = radix_to_swp_entry(page); - page = find_get_page(swap_address_space(swp), - swp_offset(swp)); + struct swap_info_struct *si; + + /* Prevent swap device to being swapoff under us */ + si = get_swap_device(swp); + if (si) { + page = find_get_page(swap_address_space(swp), + swp_offset(swp)); + put_swap_device(si); + } else + page = NULL; } } else page = find_get_page(mapping, pgoff); -- 2.20.1