From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1901C63777 for ; Sat, 21 Nov 2020 16:13:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C95B20936 for ; Sat, 21 Nov 2020 16:13:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726392AbgKUQJs (ORCPT ); Sat, 21 Nov 2020 11:09:48 -0500 Received: from wnew2-smtp.messagingengine.com ([64.147.123.27]:39585 "EHLO wnew2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725914AbgKUQJr (ORCPT ); Sat, 21 Nov 2020 11:09:47 -0500 Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailnew.west.internal (Postfix) with ESMTP id 8B045D73; Sat, 21 Nov 2020 11:09:45 -0500 (EST) Received: from mailfrontend2 ([10.202.2.163]) by compute3.internal (MEProxy); Sat, 21 Nov 2020 11:09:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm1; bh=huz5Dh VGIoT2g9v8/zblY/2WU9UNWjC3Gk6t7/f3xxM=; b=HjcgaItDtOjMydkE2UkT2C n+C8mjKYwU5H6Q66922FFvagUGKlwx/VjvjEx3+r4/1eFOq4Co6G7c08txulgj/l ZlAlGf7VCt3KxpUDRBj8nOhkax3mS2LIQ/kZ1IxRan0JBuppGlyV4NtFbL/DGa7Z TbC/QXFofb6xPc5+4+vBkLjp17wCdCMSzk7LX7rAD5q+naUn1n2+kNVKiOHIEyXU 7rpM6b0jJnd9aK3k/tlsEJsWqIXOe78T6JMfhQXpLH8nJFjOuf1yOSuOBxdN16cC c+KNMx8ya3hmZlUsGSz4N6bmDFI1t/N0jAdp8mx4/4GnuqDwB+wEReCoChMoFcmA == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedujedrudegvddgkeehucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvffukfhfgggtuggjsehttdertddttddvnecuhfhrohhmpefkughoucfu tghhihhmmhgvlhcuoehiughoshgthhesihguohhstghhrdhorhhgqeenucggtffrrghtth gvrhhnpedtffekkeefudffveegueejffejhfetgfeuuefgvedtieehudeuueekhfduheel teenucfkphepkeegrddvvdelrdduheegrddugeejnecuvehluhhsthgvrhfuihiivgeptd enucfrrghrrghmpehmrghilhhfrhhomhepihguohhstghhsehiughoshgthhdrohhrgh X-ME-Proxy: Received: from localhost (igld-84-229-154-147.inter.net.il [84.229.154.147]) by mail.messagingengine.com (Postfix) with ESMTPA id 2F31F3064AAE; Sat, 21 Nov 2020 11:09:44 -0500 (EST) Date: Sat, 21 Nov 2020 18:09:41 +0200 From: Ido Schimmel To: Aleksandr Nogikh , fw@strlen.de Cc: davem@davemloft.net, kuba@kernel.org, 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: <20201121160941.GA485907@shredder.lan> References: <20201029173620.2121359-1-aleksandrnogikh@gmail.com> <20201029173620.2121359-3-aleksandrnogikh@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201029173620.2121359-3-aleksandrnogikh@gmail.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org + 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? Thanks [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