From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 129E11DDC19 for ; Mon, 2 Dec 2024 22:05:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733177121; cv=none; b=VLRKGo3oeSOhld5agKWVQUg5K0+1Pr5wkRv3QMtx9RwvU415i9uCNWWEeg7R43zK2ctL2FFPzkj3yvDNF7YY5d4iJoyygc43LFJV18Z8lUbE8Hl86Mn7vXk0IT9UYwbCHbwzA0AsLlLtN097w7ymxLyGpLyRYsGGdqodfJoqkD4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733177121; c=relaxed/simple; bh=vguK+nhOgpergLPRZKY1wPhU8V2oi9CQ72zRGKeWH38=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=gtlQqAH/wTSq6Ncql8VUxFFx5vBogYnb7O9+K46Y4qi6k+hrrpTbwWUwMsl9wumg9BCvQ+is7bH5o6ZPdAAwk0zvL+VlS3vEmKIFXMhSlXNa1Lmaqz2VDfCEHlUjnPzousvxlToFPI6nD0ZAEBEp7Ur3nMY+PjJYSJDjkhp1oNA= 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=lEnKwJ02; arc=none smtp.client-ip=91.218.175.178 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="lEnKwJ02" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1733177116; 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=7RBDlNlOFBiB94vgvJy4Vo05/3HZNoetqya71E7uYi4=; b=lEnKwJ02p0e0GVPZ4WPr6qtO4A5fpafFOLgoxpgsgwXEmsMoG7Z2oEvDw87f6PV7BsnyQ4 qQ/UVJpgPbaPNS1XOqBJxCCp+d3/16WzK4QiyYAGwMUfolN7d9mPoV2bnib0dosWPp9+N6 DvxjurG3exfU2nXAQOF/ySyn4CA4Iqg= Date: Mon, 2 Dec 2024 14:05:05 -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() X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau To: Shigeru Yoshida Cc: Stanislav Fomichev , 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> <80d8c4cf-2897-4385-b849-2dbac863ee39@linux.dev> Content-Language: en-US In-Reply-To: <80d8c4cf-2897-4385-b849-2dbac863ee39@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 12/2/24 1:38 PM, Martin KaFai Lau wrote: > 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); > - just noticed the xdp_cpumap_attach test failed also. The test needs an adjustment in the .data_in and .data_size_in to have at least ETH_HLEN. pw-bot: cr