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[198.145.29.99]) by mx.google.com with ESMTPS id a10si3438105pfc.215.2019.07.18.21.10.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 21:10:36 -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=MCIj12XQ; 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 A398421872; Fri, 19 Jul 2019 04:10:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563509435; bh=ND04iyBGZU9uwTapA7OgOZosgZe0ucRFwjwX9sHc5uY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MCIj12XQF6u63qiSX5RXWmaW9rKHW7Wra8X0q4FPLxtfRxLOGi3tmIDOGY6wXsX9A nheKMhXt3M/2P3SolXApYLyQbEurGzrU2eWzosv57v0aENCMfp/eyVx3fYrU6SEtB9 5xVwSRsBTfgsxWONr58FV+QNWxMrVClMtqfphfEY= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andy Lutomirski , Kees Cook , Andrew Morton , Florian Weimer , Jann Horn , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 4.19 091/101] mm/gup.c: remove some BUG_ONs from get_gate_page() Date: Fri, 19 Jul 2019 00:07:22 -0400 Message-Id: <20190719040732.17285-91-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190719040732.17285-1-sashal@kernel.org> References: <20190719040732.17285-1-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: Andy Lutomirski [ Upstream commit b5d1c39f34d1c9bca0c4b9ae2e339fbbe264a9c7 ] If we end up without a PGD or PUD entry backing the gate area, don't BUG -- just fail gracefully. It's not entirely implausible that this could happen some day on x86. It doesn't right now even with an execute-only emulated vsyscall page because the fixmap shares the PUD, but the core mm code shouldn't rely on that particular detail to avoid OOPSing. Link: http://lkml.kernel.org/r/a1d9f4efb75b9d464e59fd6af00104b21c58f6f7.1561610798.git.luto@kernel.org Signed-off-by: Andy Lutomirski Reviewed-by: Kees Cook Reviewed-by: Andrew Morton Cc: Florian Weimer Cc: Jann Horn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/gup.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 43c71397c7ca..f3088d25bd92 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -458,11 +458,14 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, pgd = pgd_offset_k(address); else pgd = pgd_offset_gate(mm, address); - BUG_ON(pgd_none(*pgd)); + if (pgd_none(*pgd)) + return -EFAULT; p4d = p4d_offset(pgd, address); - BUG_ON(p4d_none(*p4d)); + if (p4d_none(*p4d)) + return -EFAULT; pud = pud_offset(p4d, address); - BUG_ON(pud_none(*pud)); + if (pud_none(*pud)) + return -EFAULT; pmd = pmd_offset(pud, address); if (!pmd_present(*pmd)) return -EFAULT; -- 2.20.1