From patchwork Mon Sep 26 15:09:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hawkins Jiawei X-Patchwork-Id: 12989058 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D270C07E9D for ; Mon, 26 Sep 2022 16:20:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236766AbiIZQUw (ORCPT ); Mon, 26 Sep 2022 12:20:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49514 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236716AbiIZQU0 (ORCPT ); Mon, 26 Sep 2022 12:20:26 -0400 Received: from mail-pf1-x432.google.com (mail-pf1-x432.google.com [IPv6:2607:f8b0:4864:20::432]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB015F8593; Mon, 26 Sep 2022 08:09:14 -0700 (PDT) Received: by mail-pf1-x432.google.com with SMTP id a80so7001082pfa.4; Mon, 26 Sep 2022 08:09:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date; bh=eWFU6eAPtlxOi+MtboPOo9H3JxiX/XlJ6GW9CbAvjgo=; b=jEmp1M4byhfqGcUfraVdUnvy/5wD9gvOg+IwIx1GNirEVr2IeRMoWHo2T/FlDdrXt0 +2JqFLi7CobaY3+Z9Y7tTeS7/3N3KOX7zld/uaLMjjsKTyPv/cQuYnwHowX77zDFCFZw I7ipjfvoN7PNigy6acM11Iv/FfFqzNJIdmz0RYWLHzIS1TUGkAO25Wa+SycZ/lDzMiMp CcZrfp+mhQLJ1bYnkeF2jpuuXetJPtk/+uZghzX4tnN4+12Hl43NjbqN8afikxIIqZj5 KT6OK/jfk415LJrTtjZgLg/RIrwdNd/tuP6Xtldhkgjb0y6Tu4WIn5KwOLUXFWvnApR2 /yfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date; bh=eWFU6eAPtlxOi+MtboPOo9H3JxiX/XlJ6GW9CbAvjgo=; b=yJgdxDYv+o5sxKEmplOa0O5ZAAgbuEzFNImqJFTGvxuYhCNu6dnbGMZUb8vEMW3opG RqbjXRr/ZilV8oaZRjw4WzzYjvwoxD/GW8Y/EDVjOUNUsCXMZxjCkCdn9wI6Muy99Zgk YhW89vdbt6rz1avJf0k/Ykhn5hP8B0V4rnUy/bCig7BakB9CkoOCfnN3xBCem2Dr3Mxh 3Vw7Ej7OT5bD7zHaMplyOiuWMEuS1Fp0DZ/pt72jib+unNcEmB8hbvM+k7UpQOU1VTsv 4g8/D4x+fJQq+z7LE6QPuJJr4U3E1tBUIc9fZ0+Yc4mBfcrneSN+KVSw5E3xArZiSY/2 Pm3g== X-Gm-Message-State: ACrzQf0cftiE6xY9tN/G6p0OA09pk94iPCuLmK6o21mG9ta+WpSb9yPt R2h9gCoHzN8+S3iu30Y8bfo= X-Google-Smtp-Source: AMsMyM5U3e5OioWTKbob8b0CuJRUM8TOHm/boiCJE7bQMIiaalfnduQo5NVE4mE+ayR6ppNhv+FQAQ== X-Received: by 2002:a05:6a00:1c72:b0:543:239c:b602 with SMTP id s50-20020a056a001c7200b00543239cb602mr24376121pfw.75.1664204953585; Mon, 26 Sep 2022 08:09:13 -0700 (PDT) Received: from localhost ([223.104.3.28]) by smtp.gmail.com with ESMTPSA id y136-20020a62648e000000b00540f96b7936sm12302173pfb.30.2022.09.26.08.09.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Sep 2022 08:09:13 -0700 (PDT) From: Hawkins Jiawei To: syzbot+473754e5af963cf014cf@syzkaller.appspotmail.com, Johannes Berg , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, 18801353760@163.com, yin31149@gmail.com, Kees Cook Subject: [PATCH] wext: use flex array destination for memcpy() Date: Mon, 26 Sep 2022 23:09:06 +0800 Message-Id: <20220926150907.8551-1-yin31149@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <00000000000070db2005e95a5984@google.com> References: <00000000000070db2005e95a5984@google.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Syzkaller reports refcount bug as follows: ------------[ cut here ]------------ memcpy: detected field-spanning write (size 8) of single field "&compat_event->pointer" at net/wireless/wext-core.c:623 (size 4) WARNING: CPU: 0 PID: 3607 at net/wireless/wext-core.c:623 wireless_send_event+0xab5/0xca0 net/wireless/wext-core.c:623 Modules linked in: CPU: 1 PID: 3607 Comm: syz-executor659 Not tainted 6.0.0-rc6-next-20220921-syzkaller #0 [...] Call Trace: ioctl_standard_call+0x155/0x1f0 net/wireless/wext-core.c:1022 wireless_process_ioctl+0xc8/0x4c0 net/wireless/wext-core.c:955 wext_ioctl_dispatch net/wireless/wext-core.c:988 [inline] wext_ioctl_dispatch net/wireless/wext-core.c:976 [inline] wext_handle_ioctl+0x26b/0x280 net/wireless/wext-core.c:1049 sock_ioctl+0x285/0x640 net/socket.c:1220 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] Wireless events will be sent on the appropriate channels in wireless_send_event(). Different wireless events may have different payload structure and size, so kernel uses **len** and **cmd** field in struct __compat_iw_event as wireless event common LCP part, uses **pointer** as a label to mark the position of remaining different part. Yet the problem is that, **pointer** is a compat_caddr_t type, which may be smaller than the relative structure at the same position. So during wireless_send_event() tries to parse the wireless events payload, it may trigger the memcpy() run-time destination buffer bounds checking when the relative structure's data is copied to the position marked by **pointer**. This patch solves it by introducing flexible-array field **ptr_bytes**, to mark the position of the wireless events remaining part next to LCP part. What's more, this patch also adds **ptr_len** variable in wireless_send_event() to improve its maintainability. Reported-and-tested-by: syzbot+473754e5af963cf014cf@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/00000000000070db2005e95a5984@google.com/ Suggested-by: Kees Cook Signed-off-by: Hawkins Jiawei Reviewed-by: Kees Cook --- include/linux/wireless.h | 10 +++++++++- net/wireless/wext-core.c | 17 ++++++++++------- 2 files changed, 19 insertions(+), 8 deletions(-) diff --git a/include/linux/wireless.h b/include/linux/wireless.h index 2d1b54556eff..e6e34d74dda0 100644 --- a/include/linux/wireless.h +++ b/include/linux/wireless.h @@ -26,7 +26,15 @@ struct compat_iw_point { struct __compat_iw_event { __u16 len; /* Real length of this stuff */ __u16 cmd; /* Wireless IOCTL */ - compat_caddr_t pointer; + + union { + compat_caddr_t pointer; + + /* we need ptr_bytes to make memcpy() run-time destination + * buffer bounds checking happy, nothing special + */ + DECLARE_FLEX_ARRAY(__u8, ptr_bytes); + }; }; #define IW_EV_COMPAT_LCP_LEN offsetof(struct __compat_iw_event, pointer) #define IW_EV_COMPAT_POINT_OFF offsetof(struct compat_iw_point, length) diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c index 76a80a41615b..fe8765c4075d 100644 --- a/net/wireless/wext-core.c +++ b/net/wireless/wext-core.c @@ -468,6 +468,7 @@ void wireless_send_event(struct net_device * dev, struct __compat_iw_event *compat_event; struct compat_iw_point compat_wrqu; struct sk_buff *compskb; + int ptr_len; #endif /* @@ -582,6 +583,9 @@ void wireless_send_event(struct net_device * dev, nlmsg_end(skb, nlh); #ifdef CONFIG_COMPAT hdr_len = compat_event_type_size[descr->header_type]; + + /* ptr_len is remaining size in event header apart from LCP */ + ptr_len = hdr_len - IW_EV_COMPAT_LCP_LEN; event_len = hdr_len + extra_len; compskb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC); @@ -612,16 +616,15 @@ void wireless_send_event(struct net_device * dev, if (descr->header_type == IW_HEADER_TYPE_POINT) { compat_wrqu.length = wrqu->data.length; compat_wrqu.flags = wrqu->data.flags; - memcpy(&compat_event->pointer, - ((char *) &compat_wrqu) + IW_EV_COMPAT_POINT_OFF, - hdr_len - IW_EV_COMPAT_LCP_LEN); + memcpy(compat_event->ptr_bytes, + ((char *)&compat_wrqu) + IW_EV_COMPAT_POINT_OFF, + ptr_len); if (extra_len) - memcpy(((char *) compat_event) + hdr_len, - extra, extra_len); + memcpy(&compat_event->ptr_bytes[ptr_len], + extra, extra_len); } else { /* extra_len must be zero, so no if (extra) needed */ - memcpy(&compat_event->pointer, wrqu, - hdr_len - IW_EV_COMPAT_LCP_LEN); + memcpy(compat_event->ptr_bytes, wrqu, ptr_len); } nlmsg_end(compskb, nlh);