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=-9.0 required=3.0 tests=DATE_IN_PAST_06_12, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 63B6FC49ED6 for ; Mon, 9 Sep 2019 22:17:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33C5721D82 for ; Mon, 9 Sep 2019 22:17:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568067463; bh=mvLCPdH8ks+yBxxce7wpWGFYX0C27A1EL9Rft6B6j8A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=EzO+vYUKSUGyF6Gt6RSrZSzoUf8ieLjm7X9RfqijQJ6ycQ6+hjR2UKbUzbK0ii12W S71LQFNL85Yvj3xXK1+dmMuihDYnMoi8ol9YZaAXfYYIrE+WsH2psw2+uoZBqvTEsO 1utYujPwPB1lGL4RJbRoTb8MYlqqnf8p0IpsDKtw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406401AbfIIWRg (ORCPT ); Mon, 9 Sep 2019 18:17:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:46826 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406390AbfIIWRf (ORCPT ); Mon, 9 Sep 2019 18:17:35 -0400 Received: from sasha-vm.mshome.net (unknown [62.28.240.114]) (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 58A2221A4A; Mon, 9 Sep 2019 22:17:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568067455; bh=mvLCPdH8ks+yBxxce7wpWGFYX0C27A1EL9Rft6B6j8A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZNg+e69h8YI4OH6y3c6cMVHzt4QpZ25sub5MT+DpEbUxOSTqtllSix42g1e/ZpAP2 A1VVHr5CZJFIwmtuX0JhlGCNpF262B6KJVnpEUQxdSi54iTqpoFH25cMrV1yKZPpwo qTzc0O8UV40hD0SKNuEfWkzvqqA08xqHakXoGCUU= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Hillf Danton , Sachin Sant , David Howells , Linus Torvalds , Sasha Levin , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 2/2] keys: Fix missing null pointer check in request_key_auth_describe() Date: Mon, 9 Sep 2019 11:42:21 -0400 Message-Id: <20190909154221.31473-2-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190909154221.31473-1-sashal@kernel.org> References: <20190909154221.31473-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Hillf Danton [ Upstream commit d41a3effbb53b1bcea41e328d16a4d046a508381 ] If a request_key authentication token key gets revoked, there's a window in which request_key_auth_describe() can see it with a NULL payload - but it makes no check for this and something like the following oops may occur: BUG: Kernel NULL pointer dereference at 0x00000038 Faulting instruction address: 0xc0000000004ddf30 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP [...] request_key_auth_describe+0x90/0xd0 LR [...] request_key_auth_describe+0x54/0xd0 Call Trace: [...] request_key_auth_describe+0x54/0xd0 (unreliable) [...] proc_keys_show+0x308/0x4c0 [...] seq_read+0x3d0/0x540 [...] proc_reg_read+0x90/0x110 [...] __vfs_read+0x3c/0x70 [...] vfs_read+0xb4/0x1b0 [...] ksys_read+0x7c/0x130 [...] system_call+0x5c/0x70 Fix this by checking for a NULL pointer when describing such a key. Also make the read routine check for a NULL pointer to be on the safe side. [DH: Modified to not take already-held rcu lock and modified to also check in the read routine] Fixes: 04c567d9313e ("[PATCH] Keys: Fix race between two instantiators of a key") Reported-by: Sachin Sant Signed-off-by: Hillf Danton Signed-off-by: David Howells Tested-by: Sachin Sant Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- security/keys/request_key_auth.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index 8882b729924dd..976deea0569e3 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -71,6 +71,9 @@ static void request_key_auth_describe(const struct key *key, { struct request_key_auth *rka = key->payload.data[0]; + if (!rka) + return; + seq_puts(m, "key:"); seq_puts(m, key->description); if (key_is_positive(key)) @@ -88,6 +91,9 @@ static long request_key_auth_read(const struct key *key, size_t datalen; long ret; + if (!rka) + return -EKEYREVOKED; + datalen = rka->callout_len; ret = datalen; -- 2.20.1