From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anmol Karn Subject: [Linux-kernel-mentees] [PATCH v2 net] rose: Fix Null pointer dereference in rose_send_frame() Date: Thu, 5 Nov 2020 21:26:00 +0530 Message-ID: <20201105155600.9711-1-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=0TyRW4uWJJtZcAW80DlztYPoMgVPukL6fuFYNjjkzDE=; b=CwLJVzbYeqMzwKr8N4c0irQdu/f97dx0RKkTorEdzvvTffs+0V8F7lfwdH4jpz7v0V 4hY8MG81Xn4RgMBDNj5Icl/qMMibAXHmp1sdvvMX4IYVBQ32MFzzbGwAkT/mJhdHZy3L eHToAsxrCiRFUC15wNY0WrGDOavL5b3+xW5jaORefVxjMmZOk9Hka9w8tzBeeuas/jAT htExxA1jMPlWsGImkT25mD8uMsWLarf5hglLSBrLETRPtJiBpRSAZV49spj9nX1XcyUF QDrnaYexaB3zFCCVfGwFS4xNDa47SImXc8JBORQhIHNcQ6BaqZAopm5n30JhAaKZ1F9d 1t3Q== List-ID: Content-Type: text/plain; charset="us-ascii" To: ralf@linux-mips.org, davem@davemloft.net, kuba@kernel.org Cc: gregkh@linuxfoundation.org, 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 rose_send_frame() dereferences `neigh->dev` when called from rose_transmit_clear_request(), and the first occurance of the `neigh` is in rose_loopback_timer() as `rose_loopback_neigh`, and it is initialized in rose_add_loopback_neigh() as NULL. i.e when `rose_loopback_neigh` used in rose_loopback_timer() its `->dev` was still NULL and rose_loopback_timer() was calling rose_rx_call_request() without checking for NULL. - net/rose/rose_link.c This bug seems to get triggered in this line: rose_call = (ax25_address *)neigh->dev->dev_addr; Fix it by adding NULL checking for `rose_loopback_neigh->dev` in rose_loopback_timer(). Reported-and-tested-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3 Signed-off-by: Anmol Karn --- net/rose/rose_loopback.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c index 7b094275ea8b..cd7774cb1d07 100644 --- a/net/rose/rose_loopback.c +++ b/net/rose/rose_loopback.c @@ -96,7 +96,7 @@ static void rose_loopback_timer(struct timer_list *unused) } if (frametype == ROSE_CALL_REQUEST) { - if ((dev = rose_dev_get(dest)) != NULL) { + if (rose_loopback_neigh->dev && (dev = rose_dev_get(dest)) != NULL) { if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0) kfree_skb(skb); } else { -- 2.29.2