From mboxrd@z Thu Jan 1 00:00:00 1970 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 35620210184; Mon, 7 Apr 2025 19:09:53 +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=1744052994; cv=none; b=gw4H0DTxkQdt8nSYf1q8pb1FFSLn27TJtDeXPSPxPZidpOtpHErB0kyaKQuSQ0R2fsMyZPqBWMCRjivyktdcBwsMcWfDUHK4u5zNmwMS+njE5jfSbcfTQhDfffiHQMgARLoAVYLpU/aChuHYKWZhDsirhroBoGstPmBovQBwIpo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744052994; c=relaxed/simple; bh=fpQyq5EzJqQT1ZD0Aov9HxzXKtuloe3+w6tId6ZagEY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZzQq2Bdnzua/S5aQ6fUXyjOsE82JaE5Fkp+4QMnk/SlH/xTO/KG4bGfijXuqrOl1Am+V4zvx/cqhmfj6qrT2sgE4+BZP1VhtIRNeRbfnT4pHFhg4FvfrJVlPndzYuE/8tzluvEFlCdgN8Mo+Zp9LTFdq6LWEG+R0Z1TUKuEI4m0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CV8+fnxX; 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="CV8+fnxX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B5E3DC4CEDD; Mon, 7 Apr 2025 19:09:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744052993; bh=fpQyq5EzJqQT1ZD0Aov9HxzXKtuloe3+w6tId6ZagEY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CV8+fnxXnyi4rIcxP6Mcw4tLItTqFZCykY0ZZrOLEruXei7/I7Qqd+//Rs3pULiKb 36WQVH/k5y1q28v+j3fJ32gz5KZmhBFvCgwMkEAaRbb32F/M0Dbfmd71m30ubsUYKK 7Vlpxue34ozpD84lFs2/l7N5LbW8kWHZJEjXl4w9UOBBrcxPgdx4nZiTsZAOaeX4nq WcJfdJ34QI/6oso0O+3iuHNgA48QFZFIHORsI5h5ejBi7AblkIAC0sPyF4HkfHujHN kColYfdHdInDIbTHDXMqIwGyWy7qj0mOBq7oIdPCg4FrHx7AkNwsMbjDSkbsUSOWh0 8BMHWRtqQgioQ== Date: Mon, 7 Apr 2025 12:09:50 -0700 From: Kees Cook To: "Gustavo A. R. Silva" Cc: Krzysztof Kozlowski , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH][next] w1: Avoid -Wflex-array-member-not-at-end warnings Message-ID: <202504071203.1024EFE5@keescook> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Mar 27, 2025 at 10:59:04AM -0600, Gustavo A. R. Silva wrote: > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are > getting ready to enable it, globally. > > Use the `DEFINE_RAW_FLEX()` helper for on-stack definitions of > a flexible structure where the size of the flexible-array member > is known at compile-time, and refactor the rest of the code, > accordingly. > > So, with these changes, fix the following warnings: > > drivers/w1/w1_netlink.c:198:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/w1/w1_netlink.c:219:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > Signed-off-by: Gustavo A. R. Silva > --- > drivers/w1/w1_netlink.c | 41 +++++++++++++++++++---------------------- > 1 file changed, 19 insertions(+), 22 deletions(-) > > diff --git a/drivers/w1/w1_netlink.c b/drivers/w1/w1_netlink.c > index 691978cddab7..845d66ab7e89 100644 > --- a/drivers/w1/w1_netlink.c > +++ b/drivers/w1/w1_netlink.c > @@ -194,16 +194,16 @@ static void w1_netlink_queue_status(struct w1_cb_block *block, > static void w1_netlink_send_error(struct cn_msg *cn, struct w1_netlink_msg *msg, > int portid, int error) > { > - struct { > - struct cn_msg cn; > - struct w1_netlink_msg msg; > - } packet; > - memcpy(&packet.cn, cn, sizeof(packet.cn)); > - memcpy(&packet.msg, msg, sizeof(packet.msg)); > - packet.cn.len = sizeof(packet.msg); > - packet.msg.len = 0; > - packet.msg.status = (u8)-error; > - cn_netlink_send(&packet.cn, portid, 0, GFP_KERNEL); > + DEFINE_RAW_FLEX(struct cn_msg, packet, data, > + sizeof(struct w1_netlink_msg)); > + struct w1_netlink_msg *pkt_msg = (struct w1_netlink_msg *)packet->data; I'm starting to think we need a helper for "DEFINE_RAW_FLEX with a trailing structure" for these. :) Anyway, conversion looks good... structs are packed, so alignment issues are unchanged. > + > + memcpy(packet, cn, sizeof(*packet)); > + memcpy(pkt_msg, msg, sizeof(*pkt_msg)); These could just be: *packet = *cn; *pkg_msg = *msg; But that was always true. The memcpy() style is retained. But it would catch type mismatches (like is accidentally introduced below). > + packet->len = sizeof(*pkt_msg); > + pkt_msg->len = 0; > + pkt_msg->status = (u8)-error; > + cn_netlink_send(packet, portid, 0, GFP_KERNEL); > } > > /** > @@ -215,22 +215,19 @@ static void w1_netlink_send_error(struct cn_msg *cn, struct w1_netlink_msg *msg, > */ > void w1_netlink_send(struct w1_master *dev, struct w1_netlink_msg *msg) > { > - struct { > - struct cn_msg cn; > - struct w1_netlink_msg msg; > - } packet; > - memset(&packet, 0, sizeof(packet)); > + DEFINE_RAW_FLEX(struct cn_msg, packet, data, > + sizeof(struct w1_netlink_msg)); > > - packet.cn.id.idx = CN_W1_IDX; > - packet.cn.id.val = CN_W1_VAL; > + packet->id.idx = CN_W1_IDX; > + packet->id.val = CN_W1_VAL; > > - packet.cn.seq = dev->seq++; > - packet.cn.len = sizeof(*msg); > + packet->seq = dev->seq++; > + packet->len = sizeof(*msg); > > - memcpy(&packet.msg, msg, sizeof(*msg)); > - packet.msg.len = 0; > + memcpy(packet, msg, sizeof(*msg)); This memcpy() is wrong. It should be targeting packet->data. > + ((struct w1_netlink_msg *)packet->data)->len = 0; And since you need it again here, I'd recommend defining a struct w1_netlink_msg pointer similar to the first hunk. -Kees > > - cn_netlink_send(&packet.cn, 0, 0, GFP_KERNEL); > + cn_netlink_send(packet, 0, 0, GFP_KERNEL); > } > > static void w1_send_slave(struct w1_master *dev, u64 rn) > -- > 2.43.0 > -- Kees Cook