From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: [PATCH 4.14 07/46] net/rose: fix NULL ax25_cb kernel panic Date: Mon, 4 Feb 2019 11:36:38 +0100 Message-ID: <20190204103609.933218831@linuxfoundation.org> References: <20190204103608.651205056@linuxfoundation.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549277109; bh=a7pN+yP8AWDUG0qGXVrXo0EcjQXFN0HWhO/Jlk6KO+o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NmBeKylxBCVXZX4HLzaOw2VkHAlYQ0lhVEYHFUnKPhfs6C8GxBySYKwFuMX4lt4Dy HjrPIJmf1GBjdaXJkabSk7M3SEYAEkCZ6qYOYW/DJzjYMs5D3pcufeO4iMjxdd+lzF 1sOiLT32lBvce7P/42sNfZ8og/93v2An4YYvjnGs= In-Reply-To: <20190204103608.651205056@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Bernard Pidoux , Dmitry Vyukov , syzbot+1a2c456a1ea08fa5b5f7@syzkaller.appspotmail.com, "David S. Miller" , Ralf Baechle , linux-hams@vger.kernel.org, netdev@vger.kernel.org 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bernard Pidoux [ Upstream commit b0cf029234f9b18e10703ba5147f0389c382bccc ] When an internally generated frame is handled by rose_xmit(), rose_route_frame() is called: if (!rose_route_frame(skb, NULL)) { dev_kfree_skb(skb); stats->tx_errors++; return NETDEV_TX_OK; } We have the same code sequence in Net/Rom where an internally generated frame is handled by nr_xmit() calling nr_route_frame(skb, NULL). However, in this function NULL argument is tested while it is not in rose_route_frame(). Then kernel panic occurs later on when calling ax25cmp() with a NULL ax25_cb argument as reported many times and recently with syzbot. We need to test if ax25 is NULL before using it. Testing: Built kernel with CONFIG_ROSE=y. Signed-off-by: Bernard Pidoux Acked-by: Dmitry Vyukov Reported-by: syzbot+1a2c456a1ea08fa5b5f7@syzkaller.appspotmail.com Cc: "David S. Miller" Cc: Ralf Baechle Cc: Bernard Pidoux Cc: linux-hams@vger.kernel.org Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/rose/rose_route.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/net/rose/rose_route.c +++ b/net/rose/rose_route.c @@ -848,6 +848,7 @@ void rose_link_device_down(struct net_de /* * Route a frame to an appropriate AX.25 connection. + * A NULL ax25_cb indicates an internally generated frame. */ int rose_route_frame(struct sk_buff *skb, ax25_cb *ax25) { @@ -865,6 +866,10 @@ int rose_route_frame(struct sk_buff *skb if (skb->len < ROSE_MIN_LEN) return res; + + if (!ax25) + return rose_loopback_queue(skb, NULL); + frametype = skb->data[2]; lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF); if (frametype == ROSE_CALL_REQUEST &&