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=-9.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 B5C51C432C0 for ; Sat, 30 Nov 2019 20:06:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8184520732 for ; Sat, 30 Nov 2019 20:06:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="r7Jo3KUd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727201AbfK3UGJ (ORCPT ); Sat, 30 Nov 2019 15:06:09 -0500 Received: from mail-pf1-f196.google.com ([209.85.210.196]:37958 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727025AbfK3UGJ (ORCPT ); Sat, 30 Nov 2019 15:06:09 -0500 Received: by mail-pf1-f196.google.com with SMTP id x185so3569787pfc.5 for ; Sat, 30 Nov 2019 12:06:07 -0800 (PST) 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=B6HI4Har6lFqncUxKqGa6gfftrxQdSXTJWPdm4fenMw=; b=r7Jo3KUdoQde2bTzCNqIAVfvdKuuiuzvwk8a2oZfS/1B697KdYEr8TJWJVrSBAoDom tv1Ovhc62HZ3OWvBympt8PerxXI5bIR3qqGjW7rHTfE+z0n7fLABtDN+srt3Nmjz7/pP /tJnefhCXx8ae27tRWIujEGMriqSRR9RBa6NV8MZUvbsrgnppuejrZbIBjKfwqtd1Grj eg+lTflopLsNcHeg361eBs4k0Oowhy5xW5r6niqBu0nDX1v6ZG3jtnWDO4WlDyQLfWP7 /nbFSU57DtA/vikVAIOXJkTh0ryXui3DtiyfCjEsTPyDT9JrIZXYjD6UBgkez2zjRZgS wIBg== 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=B6HI4Har6lFqncUxKqGa6gfftrxQdSXTJWPdm4fenMw=; b=Hg4pWY7YI1zwrBP3+FC1oOboGQmJdxd9m+/7k0Gzd28FkQtsUWPgrp9Gy4+Spshptu SzPbDXFd3Gbeq25TnwRZ5YzknupU10bO1D/k63vZ5EDf/d4gqV85/J6GMeIJukUnu10l DNXNzF68ZUKNe2I7mI3sFvvLd+O+UhXmKQNcinATUub5+++K5GkjAPTSaAki7grRSDwP DdiXn/TXMjVnD6fGLmeOSFhQqF68ypI5Yb7laQeO8WrcLbphCEXdzWODf32/ERkYbQ1b ZT7s3TqOgGqZAFKryF0D1BYs96cZcVsgc+S9TqEYE26FAle5js8aebkIz7O3tu+9z4LS Qpyg== X-Gm-Message-State: APjAAAW2jtPsPeYA8B/qM655zkw1GuKzAd8yLMolaIN3PTfjTJ+G/L7t KbGPtT4jdM7mkoUCX80hvNN0eGpw0V0= X-Google-Smtp-Source: APXvYqwaZ1XnnYgmQCksdiPEvxzC9XtgS15ytDKvkJt7Cr6Cw95eRvJh852cc2xluppSflIeNH9j7w== X-Received: by 2002:a65:41c6:: with SMTP id b6mr22702835pgq.390.1575144367002; Sat, 30 Nov 2019 12:06:07 -0800 (PST) Received: from tw-172-25-31-76.office.twttr.net ([8.25.197.24]) by smtp.gmail.com with ESMTPSA id 143sm6012578pfz.67.2019.11.30.12.06.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 30 Nov 2019 12:06:06 -0800 (PST) From: Cong Wang To: netdev@vger.kernel.org Cc: Cong Wang , syzbot+9fe8e3f6c64aa5e5d82c@syzkaller.appspotmail.com Subject: [Patch net] netrom: fix a potential NULL pointer dereference Date: Sat, 30 Nov 2019 12:05:40 -0800 Message-Id: <20191130200540.2461-1-xiyou.wangcong@gmail.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org It is possible that the skb gets removed between skb_peek() and skb_dequeue(). So we should just check the return value of skb_dequeue(). Otherwise, skb_clone() may get a NULL pointer. Technically, this should be protected by sock lock, but netrom doesn't use it correctly. It is harder to fix sock lock than just fixing this. Reported-by: syzbot+9fe8e3f6c64aa5e5d82c@syzkaller.appspotmail.com Signed-off-by: Cong Wang --- net/netrom/nr_out.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/net/netrom/nr_out.c b/net/netrom/nr_out.c index 44929657f5b7..9491a0c02bce 100644 --- a/net/netrom/nr_out.c +++ b/net/netrom/nr_out.c @@ -131,9 +131,6 @@ void nr_kick(struct sock *sk) if (nr->condition & NR_COND_PEER_RX_BUSY) return; - if (!skb_peek(&sk->sk_write_queue)) - return; - start = (skb_peek(&nr->ack_queue) == NULL) ? nr->va : nr->vs; end = (nr->va + nr->window) % NR_MODULUS; @@ -151,6 +148,8 @@ void nr_kick(struct sock *sk) * Dequeue the frame and copy it. */ skb = skb_dequeue(&sk->sk_write_queue); + if (!skb) + return; do { if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) { -- 2.21.0