From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2DAA1C43381 for ; Sat, 16 Mar 2019 17:25:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ECB2F218E0 for ; Sat, 16 Mar 2019 17:25:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552757150; bh=8to/P3PsLhQReCP0d6TVof3iBe/fXTx0wSvTMdC9WQk=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=cd0rGGuyQUQtE6zPZsDkSb+W2mBplQCsbFdGrAysc9+C05lvEXOSR5IPJh+BuV28S 1yWkUiFZNIHuoyA11WOJn2OuI9dUrAIUs6IPXt+u5GTzAb8nWaxKDjkDIkBlsdLO6b YDQZN3A2hb5PI8gOrHljsWK4PRKZVzr/7c7hv/xk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726963AbfCPRYa (ORCPT ); Sat, 16 Mar 2019 13:24:30 -0400 Received: from mail-lj1-f196.google.com ([209.85.208.196]:32894 "EHLO mail-lj1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726629AbfCPRYa (ORCPT ); Sat, 16 Mar 2019 13:24:30 -0400 Received: by mail-lj1-f196.google.com with SMTP id z7so10599023lji.0 for ; Sat, 16 Mar 2019 10:24:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=HU0TPlqyFJBx/remsyCVpTwJHhHOt/JtHhUjMDUl0gw=; b=QweJcVpa5lsLq/Nlg1EtR6DOyxjGM5yXX89kuGbH/xTxvLp499X39O8h0cEPqLoY20 2fwd0St3HzYk0p2QBb/RLNedSsz9USvZr9qj1JdlHcIjWh1VW4fIGyXr0H5ML52lVmCt e6sYw/U1qb59OOiqbML4W+uI6/9fIk8T+9Bqw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=HU0TPlqyFJBx/remsyCVpTwJHhHOt/JtHhUjMDUl0gw=; b=dBlC+ddSPsa12NO8d98q6eN/oMVkhqp4EdVjPg2PNvDuEQ7dfaPGlTKSimtncSkWwX liS1wyuklnUKRe7s5ggmVPghfDpRLJYZIKIM5VRzwjRzmax2VgVnCoHE4IeEDNDsb70B oiAZrW8QF/H4UGmg1PTeDrhpU9Htf8KARQxpEfE5Q6ZDbymECVWKzT1HeKNDM6inElmk YT23tz5u0Rt6RGAwNG2zsc9E9vpefQWsICs2/9p3Su58Tzl+pYTfyAGFi0Ngi+scbEXp MuLfO9MsdDO+3dmyD6sxD8kih+Sj1iGI7y/i7y5rTDZQFVk0XnogqxoecWlZs88BuYL5 1gQg== X-Gm-Message-State: APjAAAWENay3zuXHVtolSR+uAk1J4a4Kn8vqrflqu+cZiqShdD80P6sk BeU7IzQ3Th1RUSHzeyYcWYymitudLXs= X-Google-Smtp-Source: APXvYqzr6uWKhGz4oKnbewmbL1n5eHICuqCy9xeBzG5isJVFu4nQFn+Rm0/PvSxMf1kV7wSXqrvc2A== X-Received: by 2002:a2e:888c:: with SMTP id k12mr5650593lji.63.1552757067568; Sat, 16 Mar 2019 10:24:27 -0700 (PDT) Received: from mail-lj1-f182.google.com (mail-lj1-f182.google.com. [209.85.208.182]) by smtp.gmail.com with ESMTPSA id g25sm1052483lfh.29.2019.03.16.10.24.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Mar 2019 10:24:26 -0700 (PDT) Received: by mail-lj1-f182.google.com with SMTP id j25so4141412lji.1 for ; Sat, 16 Mar 2019 10:24:26 -0700 (PDT) X-Received: by 2002:a2e:94ca:: with SMTP id r10mr4780377ljh.118.1552757065934; Sat, 16 Mar 2019 10:24:25 -0700 (PDT) MIME-Version: 1.0 References: <000000000000675cea057e201cbb@google.com> In-Reply-To: <000000000000675cea057e201cbb@google.com> From: Linus Torvalds Date: Sat, 16 Mar 2019 10:24:10 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: BUG: unable to handle kernel paging request in slhc_free To: syzbot Cc: David Miller , Linux List Kernel Mailing , Netdev , syzkaller-bugs@googlegroups.com, tejaswit@codeaurora.org Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Dec 28, 2018 at 6:41 PM syzbot wrote: > > Reported-by: syzbot+6c5d567447bfa30f78e2@syzkaller.appspotmail.com > > BUG: unable to handle kernel paging request at fffffffffffffff4 > RIP: slhc_free+0x30/0xb0 drivers/net/slip/slhc.c:159 > Call Trace: > sl_alloc_bufs drivers/net/slip/slip.c:196 [inline] > slip_open+0xdee/0x1107 drivers/net/slip/slip.c:821 The error handling in sl_alloc_bufs() is broken. It does slcomp = slhc_init(16, 16); if (IS_ERR(slcomp)) goto err_exit; and knows that the error case returns an error pointer, but then the 'err_exit:' code just does slhc_free(slcomp); which doesn't handle error pointers. The slhc code in general is pretty odd, presumably for some legacy reason. It does things like if ( comp == NULLSLCOMPR ) return; to compare against NULL. That's some crazy stuff. I don't think anybody really wants to bother with slip any more, and the simplest fix seems to just be to let slhc_free() handle all the error pointers that slhc_init() can return, and do something like this: drivers/net/slip/slhc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/slip/slhc.c b/drivers/net/slip/slhc.c index f4e93f5fc204..3ee19a5b03a1 100644 --- a/drivers/net/slip/slhc.c +++ b/drivers/net/slip/slhc.c @@ -153,7 +153,7 @@ slhc_init(int rslots, int tslots) void slhc_free(struct slcompress *comp) { - if ( comp == NULLSLCOMPR ) + if (IS_ERR_OR_NULL(comp)) return; if ( comp->tstate != NULLSLSTATE ) which is obviously and intentionally whitespace-damaged, but you get the idea. David? Linus