From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anmol Karn Subject: [Linux-kernel-mentees] [PATCH] net: rose: Fix Null pointer dereference in rose_send_frame() Date: Thu, 15 Oct 2020 05:47:12 +0530 Message-ID: <20201015001712.72976-1-anmol.karan123@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: 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=Q5OVoE3pJbhdauHqlTDobbIRkF4tseIWuc4U1qOzq+k=; b=A/Z6g0IJ6RJqvoV2/izYHd/zFI83zBsUvMQMKk+wJFD0U7iXs69ZqVHfm1gCLTtw1c jSXGeZxxttxmRx50ZBSCb8D+fru54qFF/caQxWmrmhVbbhq8KegiZLd150mvM7Eb+4wI 7zh92ZN0K0zA3zociLwYzzbSzZbzd4P0iCwiUAkdHM/b+QFmSigWQ3A0S/WFaarzgIbl M5UlnQZjT6+dXqdDkSqwb3hW/fAuXH3exOe4A2Plkch6mSH8ZOcM3ewVfyRmy9Rvoyjr 9k1K2GRsGyzkE0pQcl4J4Y5BDBGFuIH4Hhnq9aRv3TbZpxT6pQBHHVM2Ru7+8SIZx5UK lm4w== List-ID: Content-Type: text/plain; charset="us-ascii" To: ralf@linux-mips.org, davem@davemloft.net, kuba@kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hams@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, syzkaller-bugs@googlegroups.com, anmol.karan123@gmail.com, syzbot+a1c743815982d9496393@syzkaller.appspotmail.com In rose_send_frame(), when comparing two ax.25 addresses, it assigns rose_call to either global ROSE callsign or default port, but when the former block triggers and rose_call is assigned by (ax25_address *)neigh->dev->dev_addr, a NULL pointer is dereferenced by 'neigh' when dereferencing 'dev'. - net/rose/rose_link.c This bug seems to get triggered in this line: rose_call = (ax25_address *)neigh->dev->dev_addr; Prevent it by checking NULL condition for neigh->dev before comparing addressed for rose_call initialization. Reported-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3 Signed-off-by: Anmol Karn --- I am bit sceptical about the error return code, please suggest if anything else is appropriate in place of '-ENODEV'. net/rose/rose_link.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/rose/rose_link.c b/net/rose/rose_link.c index f6102e6f5161..92ea6a31d575 100644 --- a/net/rose/rose_link.c +++ b/net/rose/rose_link.c @@ -97,6 +97,9 @@ static int rose_send_frame(struct sk_buff *skb, struct rose_neigh *neigh) ax25_address *rose_call; ax25_cb *ax25s; + if (!neigh->dev) + return -ENODEV; + if (ax25cmp(&rose_callsign, &null_ax25_address) == 0) rose_call = (ax25_address *)neigh->dev->dev_addr; else -- 2.28.0