From nobody Mon Nov 25 21:26:15 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 59BE8218D6B; Thu, 24 Oct 2024 21:11:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729804288; cv=none; b=pY3CW80W/CFVFoki58eZF77x/8uW0/A+VTWhrV1tq80DiwWR636d8QbcmddrENGPjTlIijsHY19oHLrnnMYg0dvPrPH3X0HJhT/Nc4VD3qU1mlZaLUanW//egbEiyjZlDvwGs9uujszVRhmY2676fgJTYAfOxPaKnpSPbpR2zYE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729804288; c=relaxed/simple; bh=qQQ2lofL8ErXlVJyVkxMF6DjGz27PDYgLr96a3mHVqk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dkeBkPOQJN9LgpsrRHZ8D9/1oM/jBiNFlRsxf3KIJA7/+LOxS6tsSmMCOCeY5VpP5Dc2MM47/qtSOmUrh2cMuLXvIocpgojNIkAGceLcjYH4MBzbJ4enEWQzDbhY3E/wpAyHIkXJvQOVgUEAkVmdB+DgDirPOFIo2ZiVOJB8dZA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eF5NObvb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eF5NObvb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85CEBC4CEC7; Thu, 24 Oct 2024 21:11:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729804287; bh=qQQ2lofL8ErXlVJyVkxMF6DjGz27PDYgLr96a3mHVqk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eF5NObvb9HPWXTjcRLoFpLFIt5A+QC7aR2J38Fv2syMcG37GGMnuMeESXCA38OzZD dmd5zKmxAdCSrFnEZTg/h606f8Z1npc3j4ge5zegnJk+mJ3K7RCXu9R5DVjPWUyVbV oY9S2jBZONtEysjgFimkout5CZsoynsjcPypKI9xWlHdeUwO5eHZZK/7keahDamOst IQdWAo9VeIDeMeqMZa/HpfGcswefDUdZ3uwMnyNgULOscgKZsXOH9V+VRH9pRhHS4C 7qMrc1ImxYvaCGmvUch5EEQbDfHuaQXc1P4prvfTbpblNGJSAQz4UPPMZt7xf8feF1 162hsDKT79PvA== Date: Thu, 24 Oct 2024 15:11:24 -0600 From: "Gustavo A. R. Silva" To: Andrew Lunn , Johannes Berg , David Ahern , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" , linux-hardening@vger.kernel.org, Kees Cook , Simon Horman Subject: [PATCH v2 1/4][next] uapi: socket: Introduce struct sockaddr_legacy Message-ID: <23bd38a4bf024d4a92a8a634ddf4d5689cd3a67e.1729802213.git.gustavoars@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" We are currently working on enabling the -Wflex-array-member-not-at-end compiler option. This option has helped us detect several objects of the type `struct sockaddr` that appear in the middle of composite structures like `struct rtentry`, `struct compat_rtentry`, and others: include/uapi/linux/wireless.h:751:33: warning: structure containing a flexi= ble array member is not at the end of another structure [-Wflex-array-membe= r-not-at-end] include/uapi/linux/wireless.h:776:25: warning: structure containing a flexi= ble array member is not at the end of another structure [-Wflex-array-membe= r-not-at-end] include/uapi/linux/wireless.h:833:25: warning: structure containing a flexi= ble array member is not at the end of another structure [-Wflex-array-membe= r-not-at-end] include/uapi/linux/wireless.h:857:25: warning: structure containing a flexi= ble array member is not at the end of another structure [-Wflex-array-membe= r-not-at-end] include/uapi/linux/wireless.h:864:25: warning: structure containing a flexi= ble array member is not at the end of another structure [-Wflex-array-membe= r-not-at-end] include/uapi/linux/route.h:33:25: warning: structure containing a flexible = array member is not at the end of another structure [-Wflex-array-member-no= t-at-end] include/uapi/linux/route.h:34:25: warning: structure containing a flexible = array member is not at the end of another structure [-Wflex-array-member-no= t-at-end] include/uapi/linux/route.h:35:25: warning: structure containing a flexible = array member is not at the end of another structure [-Wflex-array-member-no= t-at-end] include/uapi/linux/if_arp.h:118:25: warning: structure containing a flexibl= e array member is not at the end of another structure [-Wflex-array-member-= not-at-end] include/uapi/linux/if_arp.h:119:25: warning: structure containing a flexibl= e array member is not at the end of another structure [-Wflex-array-member-= not-at-end] include/uapi/linux/if_arp.h:121:25: warning: structure containing a flexibl= e array member is not at the end of another structure [-Wflex-array-member-= not-at-end] include/uapi/linux/if_arp.h:126:25: warning: structure containing a flexibl= e array member is not at the end of another structure [-Wflex-array-member-= not-at-end] include/uapi/linux/if_arp.h:127:25: warning: structure containing a flexibl= e array member is not at the end of another structure [-Wflex-array-member-= not-at-end] include/net/compat.h:34:25: warning: structure containing a flexible array = member is not at the end of another structure [-Wflex-array-member-not-at-e= nd] include/net/compat.h:35:25: warning: structure containing a flexible array = member is not at the end of another structure [-Wflex-array-member-not-at-e= nd] In order to fix the warnings above, we introduce `struct sockaddr_legacy`. The intention is to use it to replace the type of several struct members in the middle of composite structures, currently of type `struct sockaddr`. These middle struct members are currently causing thousands of warnings because `struct sockaddr` contains a flexible-array member, introduced by commit b5f0de6df6dce ("net: dev: Convert sa_data to flexible array in struct sockaddr"). The new `struct sockaddr_legacy` doesn't include a flexible-array member, making it suitable for use as the type of middle members in composite structs that don't really require the flexible-array member in `struct sockaddr`, thus avoiding -Wflex-array-member-not-at-end warnings. As this new struct will live in UAPI, to avoid breaking user-space code that expects `struct sockaddr`, the `__kernel_sockaddr_legacy` macro is introduced. This macro allows us to use either `struct sockaddr` or `struct sockaddr_legacy` depending on the context in which the code is used: kernel-space or user-space. Signed-off-by: Gustavo A. R. Silva Reviewed-by: Kees Cook --- include/uapi/linux/socket.h | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h index d3fcd3b5ec53..2e179706bec4 100644 --- a/include/uapi/linux/socket.h +++ b/include/uapi/linux/socket.h @@ -35,4 +35,32 @@ struct __kernel_sockaddr_storage { #define SOCK_TXREHASH_DISABLED 0 #define SOCK_TXREHASH_ENABLED 1 =20 +typedef __kernel_sa_family_t sa_family_t; + +/* + * This is the legacy form of `struct sockaddr`. The original `struct sock= addr` + * was modified in commit b5f0de6df6dce ("net: dev: Convert sa_data to fle= xible + * array in struct sockaddr") due to the fact that "One of the worst offen= ders + * of "fake flexible arrays" is struct sockaddr". This means that the orig= inal + * `char sa_data[14]` behaved as a flexible array at runtime, so a proper + * flexible-array member was introduced. + * + * This caused several flexible-array-in-the-middle issues: + * https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wflex-arr= ay-member-not-at-end + * + * `struct sockaddr_legacy` replaces `struct sockaddr` in all instances wh= ere + * objects of this type do not appear at the end of composite structures. + */ +struct sockaddr_legacy { + sa_family_t sa_family; /* address family, AF_xxx */ + char sa_data[14]; /* 14 bytes of protocol address */ +}; + +#ifdef __KERNEL__ +# define __kernel_sockaddr_legacy sockaddr_legacy +#else +# define __kernel_sockaddr_legacy sockaddr +#endif + + #endif /* _UAPI_LINUX_SOCKET_H */ --=20 2.34.1