From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4016170800 for ; Mon, 2 Dec 2024 21:38:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733175516; cv=none; b=oAEdcPVHAv+roOvoYucK/owtOgdwEVBYItL6Gpy1mauXU4Q8loY5xfuBUznqoLPV4KXKgvFvFaDbLduSD+vSbAwcv3RypnTsqEt0ZnJwxDF28Ld0G4UIJtNAXw/+29XBXSICiZz8kPNJaTEP4G3Ez/N3FIWtnXnonqGx0VLq5Fk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733175516; c=relaxed/simple; bh=7xGM2Zv6VPSBGOYslwq6dEwS0xy0nR+0XcW8sM2oLII=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZFpqyXrXNn5onj1+bVgMew+5v8TnmC+dxS60k7wl1ezxTNaK4nK+/pp70UV75FISJQbn7wccLQuBKEsKqZ6Pk5+GlutcqQFllpwyyNTpRLB6XH6Vt90RUP9hfxKnlW/Hqv4sM+YiOmBR5do1XyauG4tO3TNAr9KDereTL6Vi0jc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=n6g7sZ4H; arc=none smtp.client-ip=95.215.58.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="n6g7sZ4H" Message-ID: <80d8c4cf-2897-4385-b849-2dbac863ee39@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1733175511; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NmXr80EokHOIDy9EV+L8W5kREfs/44BiSNhckzGGbdQ=; b=n6g7sZ4HAoxcYG1osI6uKNyWpD1HeG1S633MfEzmIhCjorSSHmOxnp/v+wfHtH3JfSReEh Gn9y3qm8M/2O1oS+huWYiDdzdS9i6SQP5CZeaeTSaW+F3mtuM8QPoixx2FaYnPZCoAyZUq 4in5gIQcmdRm0zpkTdW7/sRAUhy7AfA= Date: Mon, 2 Dec 2024 13:38:17 -0800 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf] bpf, test_run: Fix use-after-free issue in eth_skb_pkt_type() To: Stanislav Fomichev , Shigeru Yoshida Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, hawk@kernel.org, lorenzo@kernel.org, toke@redhat.com, bpf@vger.kernel.org, netdev@vger.kernel.org, syzkaller References: <20241201152735.106681-1-syoshida@redhat.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 12/2/24 8:15 AM, Stanislav Fomichev wrote: > On 12/02, Shigeru Yoshida wrote: >> KMSAN reported a use-after-free issue in eth_skb_pkt_type()[1]. The >> cause of the issue was that eth_skb_pkt_type() accessed skb's data >> that didn't contain an Ethernet header. This occurs when >> bpf_prog_test_run_xdp() passes an invalid value as the user_data >> argument to bpf_test_init(). >> >> Fix this by returning an error when user_data is less than ETH_HLEN in >> bpf_test_init(). >> >> [1] >> BUG: KMSAN: use-after-free in eth_skb_pkt_type include/linux/etherdevice.h:627 [inline] >> BUG: KMSAN: use-after-free in eth_type_trans+0x4ee/0x980 net/ethernet/eth.c:165 >> eth_skb_pkt_type include/linux/etherdevice.h:627 [inline] >> eth_type_trans+0x4ee/0x980 net/ethernet/eth.c:165 >> __xdp_build_skb_from_frame+0x5a8/0xa50 net/core/xdp.c:635 >> xdp_recv_frames net/bpf/test_run.c:272 [inline] >> xdp_test_run_batch net/bpf/test_run.c:361 [inline] >> bpf_test_run_xdp_live+0x2954/0x3330 net/bpf/test_run.c:390 >> bpf_prog_test_run_xdp+0x148e/0x1b10 net/bpf/test_run.c:1318 >> bpf_prog_test_run+0x5b7/0xa30 kernel/bpf/syscall.c:4371 >> __sys_bpf+0x6a6/0xe20 kernel/bpf/syscall.c:5777 >> __do_sys_bpf kernel/bpf/syscall.c:5866 [inline] >> __se_sys_bpf kernel/bpf/syscall.c:5864 [inline] >> __x64_sys_bpf+0xa4/0xf0 kernel/bpf/syscall.c:5864 >> x64_sys_call+0x2ea0/0x3d90 arch/x86/include/generated/asm/syscalls_64.h:322 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xd9/0x1d0 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> >> Uninit was created at: >> free_pages_prepare mm/page_alloc.c:1056 [inline] >> free_unref_page+0x156/0x1320 mm/page_alloc.c:2657 >> __free_pages+0xa3/0x1b0 mm/page_alloc.c:4838 >> bpf_ringbuf_free kernel/bpf/ringbuf.c:226 [inline] >> ringbuf_map_free+0xff/0x1e0 kernel/bpf/ringbuf.c:235 >> bpf_map_free kernel/bpf/syscall.c:838 [inline] >> bpf_map_free_deferred+0x17c/0x310 kernel/bpf/syscall.c:862 >> process_one_work kernel/workqueue.c:3229 [inline] >> process_scheduled_works+0xa2b/0x1b60 kernel/workqueue.c:3310 >> worker_thread+0xedf/0x1550 kernel/workqueue.c:3391 >> kthread+0x535/0x6b0 kernel/kthread.c:389 >> ret_from_fork+0x6e/0x90 arch/x86/kernel/process.c:147 >> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 >> >> CPU: 1 UID: 0 PID: 17276 Comm: syz.1.16450 Not tainted 6.12.0-05490-g9bb88c659673 #8 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 >> >> Fixes: be3d72a2896c ("bpf: move user_size out of bpf_test_init") >> Reported-by: syzkaller >> Signed-off-by: Shigeru Yoshida >> --- >> net/bpf/test_run.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c >> index 501ec4249fed..756250aa890f 100644 >> --- a/net/bpf/test_run.c >> +++ b/net/bpf/test_run.c >> @@ -663,7 +663,7 @@ static void *bpf_test_init(const union bpf_attr *kattr, u32 user_size, >> if (size < ETH_HLEN || size > PAGE_SIZE - headroom - tailroom) >> return ERR_PTR(-EINVAL); >> >> - if (user_size > size) >> + if (user_size < ETH_HLEN || user_size > size) >> return ERR_PTR(-EMSGSIZE); >> >> size = SKB_DATA_ALIGN(size); >> -- >> 2.47.0 >> > > I wonder whether 'size < ETH_HLEN' above is needed after your patch. > Feels like 'user_size < ETH_HLEN' supersedes it. May be fixing it by replacing the existing "size" check with "user_size" check? Seems more intuitive that checking is needed on the "user_"size instead of the "size". The "if (user_size > size)" check looks useless also. Something like this? - if (size < ETH_HLEN || size > PAGE_SIZE - headroom - tailroom) + if (user_size < ETH_HLEN || user_size > PAGE_SIZE - headroom - tailroom) return ERR_PTR(-EINVAL); - if (user_size > size) - return ERR_PTR(-EMSGSIZE); -