From patchwork Sat Jul 24 21:11:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Skripkin X-Patchwork-Id: 12397801 X-Patchwork-Delegate: kuba@kernel.org 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 088A6C4320A for ; Sat, 24 Jul 2021 21:12:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D160C60041 for ; Sat, 24 Jul 2021 21:12:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229775AbhGXUbh (ORCPT ); Sat, 24 Jul 2021 16:31:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229539AbhGXUbe (ORCPT ); Sat, 24 Jul 2021 16:31:34 -0400 Received: from mail-lf1-x12e.google.com (mail-lf1-x12e.google.com [IPv6:2a00:1450:4864:20::12e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8CE7FC061575; Sat, 24 Jul 2021 14:12:04 -0700 (PDT) Received: by mail-lf1-x12e.google.com with SMTP id y34so8217689lfa.8; Sat, 24 Jul 2021 14:12:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=akz4WOvbrA3cuPXF2MwZWYXXSucqau7Y/gPfBrEyArQ=; b=Oo/pi0szYoOooKidy/toS6SrMwYGmuimGttHsHkR+Benn8/38jxqT23LWa8MR+PP32 TFVJOQEOcuxd/dXm2vox5sDhjkqb1Hi6ShTn55jc7t2QT2jpckxgE6+YE+ypVGINOOeI 2/fUOZB15wRpuq6Xf4FIc01Wm13bZJYgTmzOMr4aAXs7Gxf6SCUd3Iu28Vr8b/NnhUxu jMo4IBQVmmvU+EtabRj2O5N0byuvECFct1oh/8qbBUKADjw+0Kfczo/jKMh9wI1vi0vk sYNbtjwQmota+HJpCtTzgR0MjKnfnFIIvn5S2ohximboAVMHhQMGBl9acHX71QrTmsKE mHgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=akz4WOvbrA3cuPXF2MwZWYXXSucqau7Y/gPfBrEyArQ=; b=e9yQLE0DiS+3o4yYse/1mBAM2Nyk3SJNkID7bIagV8tT0iZrK+MAcI5/spuHtx0YE7 4eB39xL9/L+W1qbn6xm2jWSADpV41AD+GXSNl1UUH0Rc1h1qSv1a+dWXqlinwA1txpmf 4bZqAaf6I1nZgHfTK7GUy8EEGGGJGEwibEPX6V/jRWK59bhuZ4lWL7VimM6xvpS/PUvG O6NoRfLg4nLJKMcWrm3ryAFqJwpYIv4QnQnf6b2YPUV405n6xEWv8lJl5pvBXoUg9vQl wjhpzfFlojysjdJA+Svp4qRnafZLMR2+M9YQLPoj0dDvhDFTpCSKdnMYc/TRU8q6w/1N I1rQ== X-Gm-Message-State: AOAM53124FIaEGyqONlsc57gSWfVSbbf/hRvLyApl/1hdeAR1F8TD0hp 7h38WVSAwRcSDyy5yTzfOuM= X-Google-Smtp-Source: ABdhPJwbOTrgW234nWycPTjuaAUQvh6KLZSBYPqhw7kqXWjzPn0mVZswoFfnAG+9jFA39XM6V99E9g== X-Received: by 2002:a05:6512:2152:: with SMTP id s18mr7246783lfr.124.1627161121193; Sat, 24 Jul 2021 14:12:01 -0700 (PDT) Received: from localhost.localdomain ([94.103.227.213]) by smtp.gmail.com with ESMTPSA id 68sm3605649ljf.103.2021.07.24.14.12.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 24 Jul 2021 14:12:00 -0700 (PDT) From: Pavel Skripkin To: davem@davemloft.net, kuba@kernel.org, matthieu.baerts@tessares.net, stefan@datenfreihafen.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Pavel Skripkin , syzbot+5e5a981ad7cc54c4b2b4@syzkaller.appspotmail.com Subject: [PATCH] net: llc: fix skb_over_panic Date: Sun, 25 Jul 2021 00:11:59 +0300 Message-Id: <20210724211159.32108-1-paskripkin@gmail.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Syzbot reported skb_over_panic() in llc_pdu_init_as_xid_cmd(). The problem was in wrong LCC header manipulations. Syzbot's reproducer tries to send XID packet. llc_ui_sendmsg() is doing following steps: 1. skb allocation with size = len + header size len is passed from userpace and header size is 3 since addr->sllc_xid is set. 2. skb_reserve() for header_len = 3 3. filling all other space with memcpy_from_msg() Ok, at this moment we have fully loaded skb, only headers needs to be filled. Then code comes to llc_sap_action_send_xid_c(). This function pushes 3 bytes for LLC PDU header and initializes it. Then comes llc_pdu_init_as_xid_cmd(). It initalizes next 3 bytes *AFTER* LLC PDU header and call skb_push(skb, 3). This looks wrong for 2 reasons: 1. Bytes rigth after LLC header are user data, so this function was overwriting payload. 2. skb_push(skb, 3) call can cause skb_over_panic() since all free space was filled in llc_ui_sendmsg(). (This can happen is user passed 686 len: 686 + 14 (eth header) + 3 (LLC header) = 703. SKB_DATA_ALIGN(703) = 704) So, in this patch I added 2 new private constansts: LLC_PDU_TYPE_U_XID and LLC_PDU_LEN_U_XID. LLC_PDU_LEN_U_XID is used to correctly reserve header size to handle LLC + XID case. LLC_PDU_TYPE_U_XID is used by llc_pdu_header_init() function to push 6 bytes instead of 3. And finally I removed skb_push() call from llc_pdu_init_as_xid_cmd(). This changes should not affect other parts of LLC, since after all steps we just transmit buffer. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-and-tested-by: syzbot+5e5a981ad7cc54c4b2b4@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin --- Hi, net developers! I didn't find any LLC related tests, and, I guess, there isn't any since LLC (802.2) has "Odd fixes" status in MAINTAINERS file. I guess, my patch won't break something, since patch does not touch any core code, only XID cmd path. At least, patch was tested by syzbot... I look forward to receiving your views on this code. With regards, Pavel Skripkin --- include/net/llc_pdu.h | 31 +++++++++++++++++++++++-------- net/llc/af_llc.c | 10 +++++++++- net/llc/llc_s_ac.c | 2 +- 3 files changed, 33 insertions(+), 10 deletions(-) diff --git a/include/net/llc_pdu.h b/include/net/llc_pdu.h index c0f0a13ed818..49aa79c7b278 100644 --- a/include/net/llc_pdu.h +++ b/include/net/llc_pdu.h @@ -15,9 +15,11 @@ #include /* Lengths of frame formats */ -#define LLC_PDU_LEN_I 4 /* header and 2 control bytes */ -#define LLC_PDU_LEN_S 4 -#define LLC_PDU_LEN_U 3 /* header and 1 control byte */ +#define LLC_PDU_LEN_I 4 /* header and 2 control bytes */ +#define LLC_PDU_LEN_S 4 +#define LLC_PDU_LEN_U 3 /* header and 1 control byte */ +/* header and 1 control byte and XID info */ +#define LLC_PDU_LEN_U_XID (LLC_PDU_LEN_U + sizeof(struct llc_xid_info)) /* Known SAP addresses */ #define LLC_GLOBAL_SAP 0xFF #define LLC_NULL_SAP 0x00 /* not network-layer visible */ @@ -50,9 +52,10 @@ #define LLC_PDU_TYPE_U_MASK 0x03 /* 8-bit control field */ #define LLC_PDU_TYPE_MASK 0x03 -#define LLC_PDU_TYPE_I 0 /* first bit */ -#define LLC_PDU_TYPE_S 1 /* first two bits */ -#define LLC_PDU_TYPE_U 3 /* first two bits */ +#define LLC_PDU_TYPE_I 0 /* first bit */ +#define LLC_PDU_TYPE_S 1 /* first two bits */ +#define LLC_PDU_TYPE_U 3 /* first two bits */ +#define LLC_PDU_TYPE_U_XID 4 /* private type for detecting XID commands */ #define LLC_PDU_TYPE_IS_I(pdu) \ ((!(pdu->ctrl_1 & LLC_PDU_TYPE_I_MASK)) ? 1 : 0) @@ -230,9 +233,18 @@ static inline struct llc_pdu_un *llc_pdu_un_hdr(struct sk_buff *skb) static inline void llc_pdu_header_init(struct sk_buff *skb, u8 type, u8 ssap, u8 dsap, u8 cr) { - const int hlen = type == LLC_PDU_TYPE_U ? 3 : 4; + int hlen = 4; /* default value for I and S types */ struct llc_pdu_un *pdu; + switch (type) { + case LLC_PDU_TYPE_U: + hlen = 3; + break; + case LLC_PDU_TYPE_U_XID: + hlen = 6; + break; + } + skb_push(skb, hlen); skb_reset_network_header(skb); pdu = llc_pdu_un_hdr(skb); @@ -374,7 +386,10 @@ static inline void llc_pdu_init_as_xid_cmd(struct sk_buff *skb, xid_info->fmt_id = LLC_XID_FMT_ID; /* 0x81 */ xid_info->type = svcs_supported; xid_info->rw = rx_window << 1; /* size of receive window */ - skb_put(skb, sizeof(struct llc_xid_info)); + + /* no need to push/put since llc_pdu_header_init() has already + * pushed 3 + 3 bytes + */ } /** diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c index 7180979114e4..ac5cadd02cfa 100644 --- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -98,8 +98,16 @@ static inline u8 llc_ui_header_len(struct sock *sk, struct sockaddr_llc *addr) { u8 rc = LLC_PDU_LEN_U; - if (addr->sllc_test || addr->sllc_xid) + if (addr->sllc_test) rc = LLC_PDU_LEN_U; + else if (addr->sllc_xid) + /* We need to expand header to sizeof(struct llc_xid_info) + * since llc_pdu_init_as_xid_cmd() sets 4,5,6 bytes of LLC header + * as XID PDU. In llc_ui_sendmsg() we reserved header size and then + * filled all other space with user data. If we won't reserve this + * bytes, llc_pdu_init_as_xid_cmd() will overwrite user data + */ + rc = LLC_PDU_LEN_U_XID; else if (sk->sk_type == SOCK_STREAM) rc = LLC_PDU_LEN_I; return rc; diff --git a/net/llc/llc_s_ac.c b/net/llc/llc_s_ac.c index b554f26c68ee..79d1cef8f15a 100644 --- a/net/llc/llc_s_ac.c +++ b/net/llc/llc_s_ac.c @@ -79,7 +79,7 @@ int llc_sap_action_send_xid_c(struct llc_sap *sap, struct sk_buff *skb) struct llc_sap_state_ev *ev = llc_sap_ev(skb); int rc; - llc_pdu_header_init(skb, LLC_PDU_TYPE_U, ev->saddr.lsap, + llc_pdu_header_init(skb, LLC_PDU_TYPE_U_XID, ev->saddr.lsap, ev->daddr.lsap, LLC_PDU_CMD); llc_pdu_init_as_xid_cmd(skb, LLC_XID_NULL_CLASS_2, 0); rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);