From patchwork Fri Jul 26 22:20:48 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stanislav Fomichev X-Patchwork-Id: 13743221 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-pl1-f182.google.com (mail-pl1-f182.google.com [209.85.214.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A52CE143C6A; Fri, 26 Jul 2024 22:20:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722032452; cv=none; b=ioecfSYtOwbomJdu4pz9TY6+4o9fz/4XrMY7T4/AtZeqsCHA5uYTIUe05vwlNq6+IfZwq5S+ZIS3/lanJoUAQpAVDPGEadAmw5ZGyltBjJLFAOjKrkqC/A23P9+W91m+Iz/xlafD7bLOmBltpeEWiK1ipq/zoel2jdSWMC8rCWs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722032452; c=relaxed/simple; bh=a2gUn3UJy9fWdFeUAAh9cqsl8BXd91pp4YtCKH80gYU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=MIHGde89lxlPd/yWBCmE4TbhViTj7kzBWdpqHhcvfmyvr+p46UXeUWq5EOv8rIhozy4XXVQAn+wBVP79OOe5vduUZg/Y+O/OblTjjtJG14l+zVvdjbGIuU8RKKXFvxY4dNsV47vlyPVsM38/EUReQIGu0xlxP6TC/cLxV/iENRU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=fomichev.me; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.214.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=fomichev.me Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pl1-f182.google.com with SMTP id d9443c01a7336-1fc569440e1so10413825ad.3; Fri, 26 Jul 2024 15:20:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722032449; x=1722637249; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=fhJLFDJSY+qgKMb5r3WKrRKASbs5d+B46l/MhXgWp6o=; b=YbOgeG/V3bsXKLPL2rZ5D/0HQ1mTTlt0vZIUDnml8Y1ikNEPWpAfyaFxlCFSvdej81 17aNjG29Ze7Ir/e4RVvfWD/juVeJJ//mI6k9+wzrjfjhLIp7WqIrPRR220HweR2rcZx9 xUroVv5gx/5u9t9QJDBBZ2yH5Q+hLUFrQTt7e/lpuvbIjzoCPhNyzQvYhl38RZqi8b5s W5Is+Kysby5FWiu/7PfKWrEOhlhob3QFEh5DwyT8RGJ5DwHuKEa4HkVw+duwwmkg6Fdk ixQSgGlVFOUMaTzt6aFmU6hF+e7glATc8g6+R4pVSZ0Kw/pn7D+nnsUJw0yKYPQylo/o CnkA== X-Forwarded-Encrypted: i=1; AJvYcCWhNZNpp/XXYeT57cldV08uIjaaXD+qnIGQMcENoTBdB2Gin1PNAuGCLexX7oz9/RPW6NQCQ+7XzYx6N+3cH7l+ui+yuxU0 X-Gm-Message-State: AOJu0YzgXCjd3x+NUUKHyug5tWe6F9C1iG/tDQDiSbQ81jjHzTRw1eVy flDQYzlfFsJxyvZSbbgoAhmLkgaGVXq/NeuzYKBw98cOqhQGEqngCul05wg= X-Google-Smtp-Source: AGHT+IEWZfHmIrWkSomdlfty+UV4YCj6mZe8xaWfYljwUfBo+xzhq9yUALiKcUP9QOUCw981Bz1rIw== X-Received: by 2002:a17:903:234f:b0:1fb:80cf:fc95 with SMTP id d9443c01a7336-1ff048e73c5mr13153945ad.62.1722032449416; Fri, 26 Jul 2024 15:20:49 -0700 (PDT) Received: from localhost ([2601:646:9e00:f56e:73b6:7410:eb24:cba4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fed7f2b80bsm37718855ad.205.2024.07.26.15.20.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jul 2024 15:20:48 -0700 (PDT) From: Stanislav Fomichev To: bpf@vger.kernel.org, netdev@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, haoluo@google.com, jolsa@kernel.org, Julian Schindel , Magnus Karlsson , Maciej Fijalkowski Subject: [PATCH bpf-next] xsk: Try to make xdp_umem_reg extension a bit more future-proof Date: Fri, 26 Jul 2024 15:20:48 -0700 Message-ID: <20240726222048.1397869-1-sdf@fomichev.me> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net We recently found out that extending xsk_umem_reg might be a bit complicated due to not enforcing padding to be zero [0]. Add a couple of things to make it less error-prone: 1. Remove xdp_umem_reg_v2 since its sizeof is the same as xdp_umem_reg 2. Add BUILD_BUG_ON that checks that the size of xdp_umem_reg_v1 is less than xdp_umem_reg; presumably, when we get to v2, there is gonna be a similar line to enforce that sizeof(v2) > sizeof(v1) 3. Add BUILD_BUG_ON to make sure the last field plus its size matches the overall struct size. The intent is to demonstrate that we don't have any lingering padding. 0: https://lore.kernel.org/bpf/ZqI29QE+5JnkdPmE@boxer/T/#me03113f7c2458fd08f3c4114a7a9472ac3646c98 Reported-by: Julian Schindel Cc: Magnus Karlsson Reviewed-by: Maciej Fijalkowski Signed-off-by: Stanislav Fomichev --- net/xdp/xsk.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 7e16336044b2..1140b2a120ca 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -1320,14 +1320,6 @@ struct xdp_umem_reg_v1 { __u32 headroom; }; -struct xdp_umem_reg_v2 { - __u64 addr; /* Start of packet data area */ - __u64 len; /* Length of packet data area */ - __u32 chunk_size; - __u32 headroom; - __u32 flags; -}; - static int xsk_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval, unsigned int optlen) { @@ -1371,10 +1363,19 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname, if (optlen < sizeof(struct xdp_umem_reg_v1)) return -EINVAL; - else if (optlen < sizeof(struct xdp_umem_reg_v2)) - mr_size = sizeof(struct xdp_umem_reg_v1); else if (optlen < sizeof(mr)) - mr_size = sizeof(struct xdp_umem_reg_v2); + mr_size = sizeof(struct xdp_umem_reg_v1); + + BUILD_BUG_ON(sizeof(struct xdp_umem_reg_v1) >= sizeof(struct xdp_umem_reg)); + + /* Make sure the last field of the struct doesn't have + * uninitialized padding. All padding has to be explicit + * and has to be set to zero by the userspace to make + * struct xdp_umem_reg extensible in the future. + */ + BUILD_BUG_ON(offsetof(struct xdp_umem_reg, tx_metadata_len) + + sizeof_field(struct xdp_umem_reg, tx_metadata_len) != + sizeof(struct xdp_umem_reg)); if (copy_from_sockptr(&mr, optval, mr_size)) return -EFAULT;