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: Sun, 8 Nov 2020 00:26:54 +0530 Message-ID: <20201107185654.4339-1-anmol.karan123@gmail.com> References: <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:in-reply-to:references :mime-version:content-transfer-encoding; bh=afHTW824kBEGWvvhUfZ3PFiZzmUwUob7a4RTUq6L29M=; b=o7ScU2Xor+ZuZiG+hPCasydHyXeqbZkNHK3eIs5iVsazHLeSlwETo1FzIG4JhtDPfu 8duzNH3Gvwd+jeqOSOUv8CjLncS0AQ0XShWCAEpqlNonfo9kDYvLrYqqYT+qSiDM7wX9 YZiM3TBqJ7ssVrcBtc7ccbhDYYOvXythStyjRYjxqdWbvg6vpIp4ijSGwUhxUNdAQpU/ 1ssIxh08PjgKPlPKBa7GJT6mtRWkrWNjdXNtauOgBZaW1RukvGhCa9yVPyj51/PRG8Hl Azc0iBK+GRcFrXAN54ENbhsqUUVjp8fQosN0i4gUcaP8JKulxEd3AXwJ07QlarWJKXt8 MBuQ== In-Reply-To: <20201105155600.9711-1-anmol.karan123@gmail.com> List-ID: Content-Type: text/plain; charset="us-ascii" To: ralf@linux-mips.org, davem@davemloft.net, kuba@kernel.org Cc: saeed@kernel.org, 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 occurrence 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(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com Tested-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3 Signed-off-by: Anmol Karn --- Changes in v3: - Corrected checkpatch warnings and errors (Suggested-by: Saeed Mahameed ) - Added "Fixes:" tag (Suggested-by: Saeed Mahameed ) Changes in v2: - Added NULL check in rose_loopback_timer() (Suggested-by: Greg KH ) 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..2c51756ed7bf 100644 --- a/net/rose/rose_loopback.c +++ b/net/rose/rose_loopback.c @@ -96,7 +96,8 @@ static void rose_loopback_timer(struct timer_list *unused) } if (frametype == ROSE_CALL_REQUEST) { - if ((dev = rose_dev_get(dest)) != NULL) { + dev = rose_dev_get(dest); + if (rose_loopback_neigh->dev && dev) { if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0) kfree_skb(skb); } else { - 2.29.2