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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2DABC001B0 for ; Wed, 5 Jul 2023 12:52:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231218AbjGEMwi (ORCPT ); Wed, 5 Jul 2023 08:52:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53350 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230100AbjGEMwh (ORCPT ); Wed, 5 Jul 2023 08:52:37 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E1BEFDA; Wed, 5 Jul 2023 05:52:35 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7F89261512; Wed, 5 Jul 2023 12:52:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 815CDC433C7; Wed, 5 Jul 2023 12:52:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688561554; bh=I3mgC95jaUMPNBZSpRVdhaB4W5ZRw3imLS94cfTIN9w=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=pM+mAx14x75F4hkkJXR6PkXiVnUWsGQC8FbnRxNGNykH2r9VOM3ZvgtyKiSM5NJJe Q344nEKdB6H0KVtlyK2kjrObK2dedKZnRUoThVnRrHN303hr4aWxrsA7Xe5pOmNZ/+ rFht9StA4UYUF5TcuJM8l2AV09e1DNcVYuogmKaMxROJFi372o2XogJP8Pz9TLGsYL 3XiODM7vHVwGS7h815M9qFNW4nGTVfzG7sikJS1WY5vCPLPlgm7pQyYV7x+/u4+iBe xUtL/KVl4xQt8ySYDtN8eJIELTv3YZQdmB23tT5hEtneSOslXja1NqJS9yPEf08Uss Qy1yay7xQIrZQ== Date: Wed, 5 Jul 2023 21:52:30 +0900 From: Masami Hiramatsu (Google) To: m.stachyra@samsung.com Cc: "linux-kernel@vger.kernel.org" , "linux-trace-kernel@vger.kernel.org" , "rostedt@goodmis.org" , "mhiramat@kernel.org" Subject: Re: [PATCH v2] trace: fix null pointer dereference in tracing_err_log_open() Message-Id: <20230705215230.9aafc44d8bd764b6416cf655@kernel.org> In-Reply-To: <20230704102706eucms1p30d7ecdcc287f46ad67679fc8491b2e0f@eucms1p3> References: <20230704102706eucms1p30d7ecdcc287f46ad67679fc8491b2e0f@eucms1p3> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 04 Jul 2023 12:27:06 +0200 Mateusz Stachyra wrote: > Fix an issue in function 'tracing_err_log_open'. > The function doesn't call 'seq_open' if file is opened only with > write permissions, which results in 'file->private_data' being left at null. > If we then use 'lseek' on that opened file, 'seq_lseek' dereferences > 'file->private_data' in 'mutex_lock(&m->lock)', resulting in a Kernel panic. > Writing to this node requires root privilages, therefore this bug > has very little security impact. > > Tracefs node: /sys/kernel/tracing/error_log > > Example Kernel panic: > > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000038 > Call trace: > mutex_lock+0x30/0x110 > seq_lseek+0x34/0xb8 > __arm64_sys_lseek+0x6c/0xb8 > invoke_syscall+0x58/0x13c > el0_svc_common+0xc4/0x10c > do_el0_svc+0x24/0x98 > el0_svc+0x24/0x88 > el0t_64_sync_handler+0x84/0xe4 > el0t_64_sync+0x1b4/0x1b8 > Code: d503201f aa0803e0 aa1f03e1 aa0103e9 (c8e97d02) > ---[ end trace 561d1b49c12cf8a5 ]--- > Kernel panic - not syncing: Oops: Fatal exception > Good catch! This looks good to me. Acked-by: Masami Hiramatsu (Google) Thanks! > Signed-off-by: Mateusz Stachyra > Suggested-by: Steven Rostedt > --- > kernel/trace/trace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index b04f52e7c..4529e264c 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -8146,7 +8146,7 @@ static const struct file_operations tracing_err_log_fops = { > .open = tracing_err_log_open, > .write = tracing_err_log_write, > .read = seq_read, > - .llseek = seq_lseek, > + .llseek = tracing_lseek, > .release = tracing_err_log_release, > }; > > -- > 2.25.1 -- Masami Hiramatsu (Google)