From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Westphal Subject: [PATCH net] atl1c: reserve min skb headroom Date: Fri, 20 Jul 2018 19:30:57 +0200 Message-ID: <20180720173057.11365-1-fw@strlen.de> Cc: eric.dumazet@gmail.com, Florian Westphal To: Return-path: Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:57246 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387818AbeGTSSv (ORCPT ); Fri, 20 Jul 2018 14:18:51 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Got crash report with following backtrace: BUG: unable to handle kernel paging request at ffff8801869daffe RIP: 0010:[] [] ip6_finish_output2+0x394/0x4c0 RSP: 0018:ffff880186c83a98 EFLAGS: 00010283 RAX: ffff8801869db00e ... [] ip6_finish_output+0x8c/0xf0 [] ip6_output+0x57/0x100 [] ip6_forward+0x4b9/0x840 [] ip6_rcv_finish+0x66/0xc0 [] ipv6_rcv+0x319/0x530 [] netif_receive_skb+0x1c/0x70 [] atl1c_clean+0x1ec/0x310 [atl1c] ... The bad access is in neigh_hh_output(), at skb->data - 16 (HH_DATA_MOD). atl1c driver provided skb with no headroom, so 14 bytes (ethernet header) got pulled, but then 16 are copied. Reserve NET_SKB_PAD bytes headroom, like netdev_alloc_skb(). Compile tested only; I lack hardware. Fixes: 7b7017642199 ("atl1c: Fix misuse of netdev_alloc_skb in refilling rx ring") Signed-off-by: Florian Westphal --- diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c index 94270f654b3b..7087b88550db 100644 --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c @@ -1686,6 +1686,7 @@ static struct sk_buff *atl1c_alloc_skb(struct atl1c_adapter *adapter) skb = build_skb(page_address(page) + adapter->rx_page_offset, adapter->rx_frag_size); if (likely(skb)) { + skb_reserve(skb, NET_SKB_PAD); adapter->rx_page_offset += adapter->rx_frag_size; if (adapter->rx_page_offset >= PAGE_SIZE) adapter->rx_page = NULL; -- 2.16.4