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[23.128.96.18]) by mx.google.com with ESMTP id q7si202532edr.253.2020.11.30.17.56.25; Mon, 30 Nov 2020 17:57:04 -0800 (PST) Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=AUiGXNyE; spf=pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-wireless-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726486AbgLABxc (ORCPT + 99 others); Mon, 30 Nov 2020 20:53:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:40702 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725900AbgLABxc (ORCPT ); Mon, 30 Nov 2020 20:53:32 -0500 Received: from kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com (unknown [163.114.132.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E1635207FF; Tue, 1 Dec 2020 01:52:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606787570; bh=G6N04VSxm9NBg8ZwbdFSw3JTH6KMSaJ31FSrM3w3lDc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=AUiGXNyExrYDQ4y1Vrl6cdFqBxcD1Y57xAsW0RfNwFNdcKRFSrBaVyZgZlyuYl88V 9R/ZNmrioxa+aHXmSYEYl+pvqMfQdVe6U5NZQpr/BaI6qwyGRa5RkwUrgDx6oYU5wq 0vcqjJgCBHfuEcuQXlmlkwHCLohkUdqBzgWSt+QM= Date: Mon, 30 Nov 2020 17:52:48 -0800 From: Jakub Kicinski To: Ido Schimmel Cc: Aleksandr Nogikh , fw@strlen.de, davem@davemloft.net, johannes@sipsolutions.net, edumazet@google.com, andreyknvl@google.com, dvyukov@google.com, elver@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, willemdebruijn.kernel@gmail.com, Aleksandr Nogikh , Willem de Bruijn Subject: Re: [PATCH v5 2/3] net: add kcov handle to skb extensions Message-ID: <20201130175248.7f0b5309@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com> In-Reply-To: <20201121160941.GA485907@shredder.lan> References: <20201029173620.2121359-1-aleksandrnogikh@gmail.com> <20201029173620.2121359-3-aleksandrnogikh@gmail.com> <20201121160941.GA485907@shredder.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Sat, 21 Nov 2020 18:09:41 +0200 Ido Schimmel wrote: > + Florian > > On Thu, Oct 29, 2020 at 05:36:19PM +0000, Aleksandr Nogikh wrote: > > From: Aleksandr Nogikh > > > > Remote KCOV coverage collection enables coverage-guided fuzzing of the > > code that is not reachable during normal system call execution. It is > > especially helpful for fuzzing networking subsystems, where it is > > common to perform packet handling in separate work queues even for the > > packets that originated directly from the user space. > > > > Enable coverage-guided frame injection by adding kcov remote handle to > > skb extensions. Default initialization in __alloc_skb and > > __build_skb_around ensures that no socket buffer that was generated > > during a system call will be missed. > > > > Code that is of interest and that performs packet processing should be > > annotated with kcov_remote_start()/kcov_remote_stop(). > > > > An alternative approach is to determine kcov_handle solely on the > > basis of the device/interface that received the specific socket > > buffer. However, in this case it would be impossible to distinguish > > between packets that originated during normal background network > > processes or were intentionally injected from the user space. > > > > Signed-off-by: Aleksandr Nogikh > > Acked-by: Willem de Bruijn > > [...] > > > @@ -249,6 +249,9 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, > > > > fclones->skb2.fclone = SKB_FCLONE_CLONE; > > } > > + > > + skb_set_kcov_handle(skb, kcov_common_handle()); > > Hi, > > This causes skb extensions to be allocated for the allocated skb, but > there are instances that blindly overwrite 'skb->extensions' by invoking > skb_copy_header() after __alloc_skb(). For example, skb_copy(), > __pskb_copy_fclone() and skb_copy_expand(). This results in the skb > extensions being leaked [1]. > > One possible solution is to try to patch all these instances with > skb_ext_put() before skb_copy_header(). > > Another possible solution is to convert skb_copy_header() to use > skb_ext_copy() instead of __skb_ext_copy(). It will first drop the > reference on the skb extensions of the new skb, but it assumes that > 'skb->active_extensions' is valid. This is not the case in the > skb_clone() path so we should probably zero this field in __skb_clone(). > > Other suggestions? Looking at the patch from Marco to move back to a field now I'm wondering how you run into this, Ido :D AFAIU the extension is only added if process as a KCOV handle. Are you using KCOV? > [1] > BUG: memory leak > unreferenced object 0xffff888027f9a490 (size 16): > comm "syz-executor.0", pid 1155, jiffies 4295996826 (age 66.927s) > hex dump (first 16 bytes): > 01 00 00 00 01 02 6b 6b 01 00 00 00 00 00 00 00 ......kk........ > backtrace: > [<0000000005a5f2c4>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline] > [<0000000005a5f2c4>] slab_post_alloc_hook mm/slab.h:528 [inline] > [<0000000005a5f2c4>] slab_alloc_node mm/slub.c:2891 [inline] > [<0000000005a5f2c4>] slab_alloc mm/slub.c:2899 [inline] > [<0000000005a5f2c4>] kmem_cache_alloc+0x173/0x800 mm/slub.c:2904 > [<00000000c5e43ea9>] __skb_ext_alloc+0x22/0x90 net/core/skbuff.c:6173 > [<000000000de35e81>] skb_ext_add+0x230/0x4a0 net/core/skbuff.c:6268 > [<000000003b7efba4>] skb_set_kcov_handle include/linux/skbuff.h:4622 [inline] > [<000000003b7efba4>] skb_set_kcov_handle include/linux/skbuff.h:4612 [inline] > [<000000003b7efba4>] __alloc_skb+0x47f/0x6a0 net/core/skbuff.c:253 > [<000000007f789b23>] skb_copy+0x151/0x310 net/core/skbuff.c:1512 > [<000000001ce26864>] mlxsw_emad_transmit+0x4e/0x620 drivers/net/ethernet/mellanox/mlxsw/core.c:585 > [<000000005c732123>] mlxsw_emad_reg_access drivers/net/ethernet/mellanox/mlxsw/core.c:829 [inline] > [<000000005c732123>] mlxsw_core_reg_access_emad+0xda8/0x1770 drivers/net/ethernet/mellanox/mlxsw/core.c:2408 > [<00000000c07840b3>] mlxsw_core_reg_access+0x101/0x7f0 drivers/net/ethernet/mellanox/mlxsw/core.c:2583 > [<000000007c47f30f>] mlxsw_reg_write+0x30/0x40 drivers/net/ethernet/mellanox/mlxsw/core.c:2603 > [<00000000675e3fc7>] mlxsw_sp_port_admin_status_set+0x8a7/0x980 drivers/net/ethernet/mellanox/mlxsw/spectrum.c:300 > [<00000000fefe35a4>] mlxsw_sp_port_stop+0x63/0x70 drivers/net/ethernet/mellanox/mlxsw/spectrum.c:537 > [<00000000c41390e8>] __dev_close_many+0x1c7/0x300 net/core/dev.c:1607 > [<00000000628c5987>] __dev_close net/core/dev.c:1619 [inline] > [<00000000628c5987>] __dev_change_flags+0x2b9/0x710 net/core/dev.c:8421 > [<000000008cc810c6>] dev_change_flags+0x97/0x170 net/core/dev.c:8494 > [<0000000053274a78>] do_setlink+0xa5b/0x3b80 net/core/rtnetlink.c:2706 > [<00000000e4085785>] rtnl_group_changelink net/core/rtnetlink.c:3225 [inline] > [<00000000e4085785>] __rtnl_newlink+0xe06/0x17d0 net/core/rtnetlink.c:3379