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[198.145.29.99]) by mx.google.com with ESMTPS id 17si19741836pfw.148.2019.05.06.22.35.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 May 2019 22:35:41 -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=iTyCt+hh; 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 E85EB2087F; Tue, 7 May 2019 05:35:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557207340; bh=BS8bQZGoB7uxBqsmLwt1/UFGaXwyTwZEytlGNIEdKnU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iTyCt+hhs6WDmtMI27GEtirrF94M2dzJBG21bV7pKRoMyZwvzfdt0IrdEKf7521xO LsWbUzjZ/+5pBbKmUYxrzFTErGpOfV5rvoDAtwpz+74akzA+kQa2pTXPy/IJFpOH9J MdZtf/xco6k/fMksoHQil6jQtOxk9plagM56F9Tg= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andrey Ryabinin , Mel Gorman , Andrew Morton , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 5.0 95/99] mm/page_alloc.c: avoid potential NULL pointer dereference Date: Tue, 7 May 2019 01:32:29 -0400 Message-Id: <20190507053235.29900-95-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190507053235.29900-1-sashal@kernel.org> References: <20190507053235.29900-1-sashal@kernel.org> MIME-Version: 1.0 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: Andrey Ryabinin [ Upstream commit 8139ad043d632c0e9e12d760068a7a8e91659aa1 ] ac.preferred_zoneref->zone passed to alloc_flags_nofragment() can be NULL. 'zone' pointer unconditionally derefernced in alloc_flags_nofragment(). Bail out on NULL zone to avoid potential crash. Currently we don't see any crashes only because alloc_flags_nofragment() has another bug which allows compiler to optimize away all accesses to 'zone'. Link: http://lkml.kernel.org/r/20190423120806.3503-1-aryabinin@virtuozzo.com Fixes: 6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation") Signed-off-by: Andrey Ryabinin Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index eedb57f9b40b..d59be95ba45c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3385,6 +3385,9 @@ alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask) alloc_flags |= ALLOC_KSWAPD; #ifdef CONFIG_ZONE_DMA32 + if (!zone) + return alloc_flags; + if (zone_idx(zone) != ZONE_NORMAL) goto out; -- 2.20.1