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=-6.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 039F0C43441 for ; Wed, 28 Nov 2018 23:19:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3A0A208E7 for ; Wed, 28 Nov 2018 23:19:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="QvPnTkvN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B3A0A208E7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-security-module-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726416AbeK2KXB (ORCPT ); Thu, 29 Nov 2018 05:23:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:43104 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726382AbeK2KXA (ORCPT ); Thu, 29 Nov 2018 05:23:00 -0500 Received: from gmail.com (unknown [104.132.1.85]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CBB25208E7; Wed, 28 Nov 2018 23:19:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1543447183; bh=G/mWoFapGnNvF++zuh02gB8xa9kZBEp+ubRIYqwRlQM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QvPnTkvNeT85/ABR9+d0CTd8KLFe4QHXPFt8Aq1ghEBaX6SfT2cWuxjclul13P+9G 7XWFwlMap/kjtI7qsjMaA36R/D2SWBG8kZW+0b0xYOP7dqp9JO4exDO+i5euLANyA9 XhKLuYCqchTwr8abeiFYpKAE7kfz9Y+de1McV5wc= Date: Wed, 28 Nov 2018 15:19:41 -0800 From: Eric Biggers To: keyrings@vger.kernel.org, David Howells Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH v2] KEYS: always initialize keyring_index_key::desc_len Message-ID: <20181128231940.GB131170@gmail.com> References: <000000000000a722550577796543@google.com> <20181103015854.7380-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181103015854.7380-1-ebiggers@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Nov 02, 2018 at 06:58:54PM -0700, Eric Biggers wrote: > From: Eric Biggers > > syzbot hit the 'BUG_ON(index_key->desc_len == 0);' in __key_link_begin() > called from construct_alloc_key() during sys_request_key(), because the > length of the key description was never calculated. > > The problem is that we rely on ->desc_len being initialized by > search_process_keyrings(), specifically by search_nested_keyrings(). > But, if the process isn't subscribed to any keyrings that never happens. > > Fix it by always initializing keyring_index_key::desc_len as soon as the > description is set, like we already do in some places. > > The following program reproduces the BUG_ON() when it's run as root and > no session keyring has been installed. If it doesn't work, try removing > pam_keyinit.so from /etc/pam.d/login and rebooting. > > #include > #include > #include > > int main(void) > { > int id = add_key("keyring", "syz", NULL, 0, KEY_SPEC_USER_KEYRING); > > keyctl_setperm(id, KEY_OTH_WRITE); > setreuid(5000, 5000); > request_key("user", "desc", "", id); > } > > Reported-by: syzbot+ec24e95ea483de0a24da@syzkaller.appspotmail.com > Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring") > Cc: # v3.13+ > Signed-off-by: Eric Biggers > --- > > v2: In proc_keys_show(), assign index_key directly > > security/keys/keyring.c | 4 +--- > security/keys/proc.c | 3 +-- > security/keys/request_key.c | 1 + > security/keys/request_key_auth.c | 2 +- > 4 files changed, 4 insertions(+), 6 deletions(-) > > diff --git a/security/keys/keyring.c b/security/keys/keyring.c > index 41bcf57e96f21..99a55145ddcd2 100644 > --- a/security/keys/keyring.c > +++ b/security/keys/keyring.c > @@ -661,9 +661,6 @@ static bool search_nested_keyrings(struct key *keyring, > BUG_ON((ctx->flags & STATE_CHECKS) == 0 || > (ctx->flags & STATE_CHECKS) == STATE_CHECKS); > > - if (ctx->index_key.description) > - ctx->index_key.desc_len = strlen(ctx->index_key.description); > - > /* Check to see if this top-level keyring is what we are looking for > * and whether it is valid or not. > */ > @@ -914,6 +911,7 @@ key_ref_t keyring_search(key_ref_t keyring, > struct keyring_search_context ctx = { > .index_key.type = type, > .index_key.description = description, > + .index_key.desc_len = strlen(description), > .cred = current_cred(), > .match_data.cmp = key_default_cmp, > .match_data.raw_data = description, > diff --git a/security/keys/proc.c b/security/keys/proc.c > index 5af2934965d80..d38be9db2cc07 100644 > --- a/security/keys/proc.c > +++ b/security/keys/proc.c > @@ -166,8 +166,7 @@ static int proc_keys_show(struct seq_file *m, void *v) > int rc; > > struct keyring_search_context ctx = { > - .index_key.type = key->type, > - .index_key.description = key->description, > + .index_key = key->index_key, > .cred = m->file->f_cred, > .match_data.cmp = lookup_user_key_possessed, > .match_data.raw_data = key, > diff --git a/security/keys/request_key.c b/security/keys/request_key.c > index 114f7408feee6..7385536986497 100644 > --- a/security/keys/request_key.c > +++ b/security/keys/request_key.c > @@ -545,6 +545,7 @@ struct key *request_key_and_link(struct key_type *type, > struct keyring_search_context ctx = { > .index_key.type = type, > .index_key.description = description, > + .index_key.desc_len = strlen(description), > .cred = current_cred(), > .match_data.cmp = key_default_cmp, > .match_data.raw_data = description, > diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c > index 424e1d90412ea..6797843154f03 100644 > --- a/security/keys/request_key_auth.c > +++ b/security/keys/request_key_auth.c > @@ -246,7 +246,7 @@ struct key *key_get_instantiation_authkey(key_serial_t target_id) > struct key *authkey; > key_ref_t authkey_ref; > > - sprintf(description, "%x", target_id); > + ctx.index_key.desc_len = sprintf(description, "%x", target_id); > > authkey_ref = search_process_keyrings(&ctx); > > -- > 2.19.1 > Ping. David, are you planning to apply this? - Eric