From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (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 385972797AC for ; Wed, 15 Apr 2026 09:40:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776246036; cv=none; b=KODcrxVZVzZLSrJa3dRksObZZAsFJXi7ilgidiXe16mFMjiADSgr4VmjePU+90A1usMcdoZXEvGVz7k24He9aiOxRwvZTq81dpfvQK0k5vqfhmluOvSK2wi9VEhA+0tUqjXINC2jM8P1oDr/ikQbrWImg4vz4WykRxyA6IohkjI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776246036; c=relaxed/simple; bh=gmAkwh6nFkvcQ9Co6O3nLw5KDAkvxL4G8X/oCpJV2uo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bO+1tMjpbzxnGIfDE6SpuVa2OHWjYzFiIODbqp8EkFlaxABFU/IR2pPILbEOR4JWgMwFNnvPZHnexCHrzw35JC/0X+HYkNUCJcljOGmaj4Rq5NW4i2cjPHhiaCrTV4NsHaTDbenaxg77hwg5IEqIAF9o3ZmphoWk+BkfIrtp4/M= 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=T880w4qM; arc=none smtp.client-ip=91.218.175.182 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="T880w4qM" Date: Wed, 15 Apr 2026 11:40:26 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1776246030; 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=s859KPZEtR/gSJZLKsqMqcDAerKq22zEODV1qkwUckA=; b=T880w4qMmr0Z0RcnHGqQiow0RWnZ38SYAprEHAv5h9kM471gEmdkWqJ1DSk1VXmXd8nBD+ TrEttB1J/mWzypy6U4hpYYEN5R/Yc8bhZhqxcoeH5UjeoxleFTZBpKY151SutTxFSbNsgl 0jlm5VWXckL7ntru5k1a6Vv+u8xbUxs= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Thorsten Blum To: Jarkko Sakkinen Cc: David Howells , Kees Cook , "Gustavo A. R. Silva" , keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH net-next 2/2] KEYS: annotate struct user_key_payload with __counted_by Message-ID: References: <20260406175810.1018681-3-thorsten.blum@linux.dev> <20260406175810.1018681-4-thorsten.blum@linux.dev> 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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT On Wed, Apr 15, 2026 at 02:58:05AM +0300, Jarkko Sakkinen wrote: > On Wed, Apr 08, 2026 at 02:21:19PM +0200, Thorsten Blum wrote: > > On Wed, Apr 08, 2026 at 12:02:25PM +0300, Jarkko Sakkinen wrote: > > > On Mon, Apr 06, 2026 at 07:58:10PM +0200, Thorsten Blum wrote: > > > > Add the __counted_by() compiler attribute to the flexible array member > > > > 'data' to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and > > > > CONFIG_FORTIFY_SOURCE. > > > > > > > > Signed-off-by: Thorsten Blum > > > > --- > > > > include/keys/user-type.h | 3 ++- > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/include/keys/user-type.h b/include/keys/user-type.h > > > > index 386c31432789..2305991f4fcd 100644 > > > > --- a/include/keys/user-type.h > > > > +++ b/include/keys/user-type.h > > > > @@ -27,7 +27,8 @@ > > > > struct user_key_payload { > > > > struct rcu_head rcu; /* RCU destructor */ > > > > unsigned short datalen; /* length of this data */ > > > > - char data[] __aligned(__alignof__(u64)); /* actual data */ > > > > + char data[] /* actual data */ > > > > + __aligned(__alignof__(u64)) __counted_by(datalen); > > > > }; > > > > > > > > extern struct key_type key_type_user; > > > > > > You don't provide any evidence of any improvement. > > > > It's a proactive hardening change to help avoid future mistakes. > > > > The __counted_by() annotation makes the bounds visible to the compiler > > and at runtime so that future ->data accesses can be checked against > > ->datalen. > > > > The current code is correct regarding ->data accesses and doesn't > > require any changes. > > OK I'll buy that but send +1 version: > > ~/work/kernel.org/jarkko/linux-tpmdd next > ❯ git am -3 20260406_thorsten_blum_keys_dns_drop_unused_upayload_data_nul_terminator.mbx > Applying: keys, dns: drop unused upayload->data NUL terminator > error: sha1 information is lacking or useless (net/dns_resolver/dns_key.c). > error: could not build fake ancestor > Patch failed at 0001 keys, dns: drop unused upayload->data NUL terminator > hint: Use 'git am --show-current-patch=diff' to see the failed patch > When you have resolved this problem, run "git am --continue". > If you prefer to skip this patch, run "git am --skip" instead. > To restore the original branch and stop patching, run "git am --abort". AFAICT, linux-tpmdd/next is missing this change: https://lore.kernel.org/all/20260226214930.785423-3-thorsten.blum@linux.dev/