From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755283AbdLLNHA (ORCPT ); Tue, 12 Dec 2017 08:07:00 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:34718 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755085AbdLLNAu (ORCPT ); Tue, 12 Dec 2017 08:00:50 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sergey Senozhatsky , Minchan Kim , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.9 133/148] zsmalloc: calling zs_map_object() from irq is a bug Date: Tue, 12 Dec 2017 13:45:43 +0100 Message-Id: <20171212124438.051767190@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171212124431.207182779@linuxfoundation.org> References: <20171212124431.207182779@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sergey Senozhatsky [ Upstream commit 1aedcafbf32b3f232c159b14cd0d423fcfe2b861 ] Use BUG_ON(in_interrupt()) in zs_map_object(). This is not a new BUG_ON(), it's always been there, but was recently changed to VM_BUG_ON(). There are several problems there. First, we use use per-CPU mappings both in zsmalloc and in zram, and interrupt may easily corrupt those buffers. Second, and more importantly, we believe it's possible to start leaking sensitive information. Consider the following case: -> process P swap out zram per-cpu mapping CPU1 compress page A -> IRQ swap out zram per-cpu mapping CPU1 compress page B write page from per-cpu mapping CPU1 to zsmalloc pool iret -> process P write page from per-cpu mapping CPU1 to zsmalloc pool [*] return * so we store overwritten data that actually belongs to another page (task) and potentially contains sensitive data. And when process P will page fault it's going to read (swap in) that other task's data. Link: http://lkml.kernel.org/r/20170929045140.4055-1-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky Acked-by: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- mm/zsmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1407,7 +1407,7 @@ void *zs_map_object(struct zs_pool *pool * pools/users, we can't allow mapping in interrupt context * because it can corrupt another users mappings. */ - WARN_ON_ONCE(in_interrupt()); + BUG_ON(in_interrupt()); /* From now on, migration cannot move the object */ pin_tag(handle);