From patchwork Wed Sep 7 01:56:18 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Ziyang Xuan (William)" X-Patchwork-Id: 12968366 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F33B6ECAAD5 for ; Wed, 7 Sep 2022 01:56:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229590AbiIGB40 (ORCPT ); Tue, 6 Sep 2022 21:56:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229493AbiIGB4Z (ORCPT ); Tue, 6 Sep 2022 21:56:25 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 962328A6F7; Tue, 6 Sep 2022 18:56:24 -0700 (PDT) Received: from canpemm500006.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4MMlcy2xBxzkYFS; Wed, 7 Sep 2022 09:52:34 +0800 (CST) Received: from localhost.localdomain (10.175.104.82) by canpemm500006.china.huawei.com (7.192.105.130) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 7 Sep 2022 09:56:22 +0800 From: Ziyang Xuan To: , , , , CC: , , , , , , Subject: [PATCH net] net: tun: limit first seg size to avoid oversized linearization Date: Wed, 7 Sep 2022 09:56:18 +0800 Message-ID: <20220907015618.2140679-1-william.xuanziyang@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.175.104.82] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500006.china.huawei.com (7.192.105.130) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Recently, we found a syzkaller problem as following: ======================================================== WARNING: CPU: 1 PID: 17965 at mm/page_alloc.c:5295 __alloc_pages+0x1308/0x16c4 mm/page_alloc.c:5295 ... Call trace: __alloc_pages+0x1308/0x16c4 mm/page_alloc.c:5295 __alloc_pages_node include/linux/gfp.h:550 [inline] alloc_pages_node include/linux/gfp.h:564 [inline] kmalloc_large_node+0x94/0x350 mm/slub.c:4038 __kmalloc_node_track_caller+0x620/0x8e4 mm/slub.c:4545 __kmalloc_reserve.constprop.0+0x1e4/0x2b0 net/core/skbuff.c:151 pskb_expand_head+0x130/0x8b0 net/core/skbuff.c:1654 __skb_grow include/linux/skbuff.h:2779 [inline] tun_napi_alloc_frags+0x144/0x610 drivers/net/tun.c:1477 tun_get_user+0x31c/0x2010 drivers/net/tun.c:1835 tun_chr_write_iter+0x98/0x100 drivers/net/tun.c:2036 It is because the first seg size of the iov_iter from user space is very big, it is 2147479538 which is bigger than the threshold value for bail out early in __alloc_pages(). And skb->pfmemalloc is true, __kmalloc_reserve() would use pfmemalloc reserves without __GFP_NOWARN flag. Thus we got a warning. I noticed that non-first segs size are required less than PAGE_SIZE in tun_napi_alloc_frags(). The first seg should not be a special case, and oversized linearization is also unreasonable. Limit the first seg size to PAGE_SIZE to avoid oversized linearization. Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver") Signed-off-by: Ziyang Xuan Acked-by: Petar Penkov --- drivers/net/tun.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 259b2b84b2b3..7db515f94667 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1454,12 +1454,12 @@ static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile, size_t len, const struct iov_iter *it) { + size_t linear = iov_iter_single_seg_count(it); struct sk_buff *skb; - size_t linear; int err; int i; - if (it->nr_segs > MAX_SKB_FRAGS + 1) + if (it->nr_segs > MAX_SKB_FRAGS + 1 || linear > PAGE_SIZE) return ERR_PTR(-EMSGSIZE); local_bh_disable(); @@ -1468,7 +1468,6 @@ static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile, if (!skb) return ERR_PTR(-ENOMEM); - linear = iov_iter_single_seg_count(it); err = __skb_grow(skb, linear); if (err) goto free;