From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from www62.your-server.de (www62.your-server.de [213.133.104.62]) (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 8636E1C20; Wed, 21 Feb 2024 16:40:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.133.104.62 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708533631; cv=none; b=RNCWtSRif23ZoZTN/nzgxHWUVMF2SC7dCdohrXb7SXUuwdilFhb9cRepdaGgF1k2wHw4vy2IIRGBHIMXO6F0iZov1S61WasAo4sawDAUMr0RG5ZoLhlo0u88GpeUr5R19VW+3oRSEueP0VHQLn3lqmBuNjaMIdZdRROIlCegLh4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708533631; c=relaxed/simple; bh=45I0J5biXwYLiUaf/PmqF1jvW/5x55RLPKwzjIKpH4I=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=cv1d4b7OiKxi8I++gZCzaLjaVyNnVOiHssqAUoJZSw8KH0AqrrY4AX+rpZvd+WMvVOspuyottxqI8e8lLaOwdnFFyhFsHtcMqQe0Nn0wBM94lFZ4sKnqt0d7YNK4bdDzNVjjkwb3F2m4TSQtpUwoZyHyXMY6fevY5zccHkuR/b8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=iogearbox.net; spf=pass smtp.mailfrom=iogearbox.net; dkim=pass (2048-bit key) header.d=iogearbox.net header.i=@iogearbox.net header.b=nxtdSMGu; arc=none smtp.client-ip=213.133.104.62 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=iogearbox.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=iogearbox.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=iogearbox.net header.i=@iogearbox.net header.b="nxtdSMGu" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=iogearbox.net; s=default2302; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID; bh=iE/w7zcXxXdaU9PL76g2DzI65P5Qvx6HEpMubn6cjls=; b=nxtdSMGuBsIvBlcGsFV4q/QyMF TgOVPrStsVJMCkxFJBEqMlQSHAzM+REezZFM0xOLRHPRXVSajD7AuVxjN89Gx8zV8VfQaROCuWJ9A hsKvkN0wOOFwEAN6pFc8y73S6NAYPyvKNlCWQfSndtOWsQDCCadb/MAydty5bhz/Zq3BFJxoh0CIR a2Ne48t1iTcE2roNaY1NWfiRbYJf8DdWNP79eI3L97P88sN1qdZL9NnF8z2INf8oE+Saj3QB2dpB0 ENlP8JXP2KoHERxkPQL1sRIBscnF0jK0so1z2Qi3PdIX6N417a9CoXAIjTLRVkK9YA2p0bewcxPbd 9aLoNtDA==; Received: from sslproxy07.your-server.de ([78.47.199.104]) by www62.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1rcpdW-0007PB-Iw; Wed, 21 Feb 2024 17:39:58 +0100 Received: from [178.197.249.13] (helo=linux.home) by sslproxy07.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1rcpdU-0005ll-2a; Wed, 21 Feb 2024 17:39:56 +0100 Subject: Re: [PATCH v4] bpf: Replace bpf_lpm_trie_key 0-length array with flexible array To: Kees Cook Cc: Mark Rutland , "Gustavo A . R . Silva" , Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , Haowen Bai , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Yonghong Song , Jonathan Corbet , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , Joanne Koong , Yafang Shao , Kui-Feng Lee , Anton Protopopov , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, netdev@vger.kernel.org, linux-hardening@vger.kernel.org References: <20240220185421.it.949-kees@kernel.org> From: Daniel Borkmann Message-ID: Date: Wed, 21 Feb 2024 17:39:55 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20240220185421.it.949-kees@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.103.10/27192/Wed Feb 21 10:23:23 2024) On 2/20/24 7:54 PM, Kees Cook wrote: > Replace deprecated 0-length array in struct bpf_lpm_trie_key with > flexible array. Found with GCC 13: > > ../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=] > 207 | *(__be16 *)&key->data[i]); > | ^~~~~~~~~~~~~ > ../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16' > 102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) > | ^ > ../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu' > 97 | #define be16_to_cpu __be16_to_cpu > | ^~~~~~~~~~~~~ > ../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu' > 206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] > ^ > | ^~~~~~~~~~~ > In file included from ../include/linux/bpf.h:7: > ../include/uapi/linux/bpf.h:82:17: note: while referencing 'data' > 82 | __u8 data[0]; /* Arbitrary size */ > | ^~~~ > > And found at run-time under CONFIG_FORTIFY_SOURCE: > > UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49 > index 0 is out of range for type '__u8 [*]' > > Changing struct bpf_lpm_trie_key is difficult since has been used by > userspace. For example, in Cilium: > > struct egress_gw_policy_key { > struct bpf_lpm_trie_key lpm_key; > __u32 saddr; > __u32 daddr; > }; > > While direct references to the "data" member haven't been found, there > are static initializers what include the final member. For example, > the "{}" here: > > struct egress_gw_policy_key in_key = { > .lpm_key = { 32 + 24, {} }, > .saddr = CLIENT_IP, > .daddr = EXTERNAL_SVC_IP & 0Xffffff, > }; > > To avoid the build time and run time warnings seen with a 0-sized > trailing array for struct bpf_lpm_trie_key, introduce a new struct > that correctly uses a flexible array for the trailing bytes, > struct bpf_lpm_trie_key_u8. As part of this, include the "header" > portion (which is just the "prefixlen" member), so it can be used > by anything building a bpf_lpr_trie_key that has trailing members that > aren't a u8 flexible array (like the self-test[1]), which is named > struct bpf_lpm_trie_key_hdr. > > Adjust the kernel code to use struct bpf_lpm_trie_key_u8 through-out, > and for the selftest to use struct bpf_lpm_trie_key_hdr. Add a comment > to the UAPI header directing folks to the two new options. > > Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/ [1] > Reported-by: Mark Rutland > Closes: https://paste.debian.net/hidden/ca500597/ > Acked-by: Gustavo A. R. Silva > Signed-off-by: Kees Cook [...] The build in BPF CI is still broken, did you try to build selftests? https://github.com/kernel-patches/bpf/actions/runs/7978647641 [...] GEN-SKEL [test_progs] linked_funcs.skel.h LINK-BPF [test_progs] test_usdt.bpf.o GEN-SKEL [test_progs-no_alu32] profiler1.skel.h GEN-SKEL [test_progs] test_usdt.skel.h In file included from /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:11, from test_cpp.cpp:4: /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:92:17: error: ‘struct bpf_lpm_trie_key_u8::::bpf_lpm_trie_key_hdr’ invalid; an anonymous union may only have public non-static data members [-fpermissive] 92 | __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */, | ^~~~~~~~~~~~~~~~~~~~ /tmp/work/bpf/bpf/tools/include/uapi/linux/stddef.h:29:10: note: in definition of macro ‘__struct_group’ 29 | struct TAG { MEMBERS } ATTRS NAME; \ | ^~~ BINARY bench make: *** [Makefile:703: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/test_cpp] Error 1 make: *** Waiting for unfinished jobs.... make: Leaving directory '/tmp/work/bpf/bpf/tools/testing/selftests/bpf' Error: Process completed with exit code 2. > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 754e68ca8744..31e9bdd4641e 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -8,6 +8,7 @@ > #ifndef _UAPI__LINUX_BPF_H__ > #define _UAPI__LINUX_BPF_H__ > > +#include > #include > #include > > @@ -77,12 +78,24 @@ struct bpf_insn { > __s32 imm; /* signed immediate constant */ > }; > > -/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */ > +/* Deprecated: use struct bpf_lpm_trie_key_u8 (when the "data" member is needed for > + * byte access) or struct bpf_lpm_trie_key_hdr (when using an alternative type for > + * the trailing flexible array member) instead. > + */ > struct bpf_lpm_trie_key { > __u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */ > __u8 data[0]; /* Arbitrary size */ > }; > > +/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry, with trailing byte array. */ > +struct bpf_lpm_trie_key_u8 { > + __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */, > + /* up to 32 for AF_INET, 128 for AF_INET6 */ > + __u32 prefixlen; > + ); > + __u8 data[]; /* Arbitrary size */ > +}; > + > struct bpf_cgroup_storage_key { > __u64 cgroup_inode_id; /* cgroup inode id */ > __u32 attach_type; /* program attach type (enum bpf_attach_type) */