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 6C21227A127; Thu, 8 May 2025 15:58:51 +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=1746719933; cv=none; b=KwCnJjf1aCA6uGgQ6WiCzvDhy6+ZIS5CDubm3TFyygM0HNAzCOOpZvyo7AletXicjz8PMfOw4YwAhUeIGFM4ff2H+b0+kFAU/o1WgC25cNJ1K0RR4/Ph2yemzWnyFLAFORRXMBGWs3Km0nJ+LJFgn8f6fYQOsjmwffgQ+5T307o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746719933; c=relaxed/simple; bh=8jYZVX0/2dxdtW2AwtBMm0nQOTU2ozp7HEs7ay7+F5g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tWWo5UVwN1fqysG/VeHzbi06yaF9wLFzibHefp6ouh4OzlMrrsTMrLntidxNvTts5Z2wspwkBben28DH4CyPnxVzKJ/p/+ZpEARYhAGe5tFG3voWQK2DeuONSmsRJWoxTQwWdiCWZZI9TQDSybHyiD9QnqcVOOhr1s0dpxexK78= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QqVYuR8f; 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="QqVYuR8f" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA38EC4CEE7; Thu, 8 May 2025 15:58:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746719931; bh=8jYZVX0/2dxdtW2AwtBMm0nQOTU2ozp7HEs7ay7+F5g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QqVYuR8f9MAE6X0M+Ea5uUkt3BwJhEeAVhK5N9Yat9xDZzbF8VVkdoMEn4Goh4A1Z ZEpAvA5i2+y0R8R7Y2mQRlht2k25qEfWDFexE6AyD/cKh0JaF9+A2sEFf9GzBJXRDj LrbHXVruSyA5zXfVv9zY2a1GaeGANKjrBwYToBymmz4qY2/i8TgtlydHsrUK/Y9lmw SCOcIhQXDgFyXLJyxoE+3APIM8l6+JueosfnWznRJVivvQ7K+uHlm4oVs0OB7LHrMr MN09X8O0PSPGs10h1UKbT9ehMf1v6HI9UUQSgCBHaJVrd7PHL25FswAC/ysHTVSeMJ d0mobG3Pwsnaw== Date: Thu, 8 May 2025 08:58:48 -0700 From: Kees Cook To: Coly Li Cc: Coly Li , Kent Overstreet , Ard Biesheuvel , linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v2] md/bcache: Mark __nonstring look-up table Message-ID: <202505080844.DD7F50F0A@keescook> References: <20250418202130.it.887-kees@kernel.org> <389A9925-0990-422C-A1B3-0195FAA73288@coly.li> <851B250D-A22C-4B47-BBAC-55284B5B5790@coly.li> 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: <851B250D-A22C-4B47-BBAC-55284B5B5790@coly.li> On Thu, May 08, 2025 at 11:01:34AM +0800, Coly Li wrote: > > > 2025年4月19日 11:55，Coly Li 写道： > > > > > > > >> 2025年4月19日 04:21，Kees Cook 写道： > >> > >> GCC 15's new -Wunterminated-string-initialization notices that the 16 > >> character lookup table "zero_uuid" (which is not used as a C-String) > >> needs to be marked as "nonstring": > >> > >> drivers/md/bcache/super.c: In function 'uuid_find_empty': > >> drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization] > >> 549 | static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"; > >> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > >> > >> Add the annotation (since it is not used as a C-String), and switch the > >> initializer to an array of bytes. > >> > >> Signed-off-by: Kees Cook > >> --- > >> v2: use byte array initializer (colyli) > >> v1: https://lore.kernel.org/all/20250416220135.work.394-kees@kernel.org/ > >> Cc: Coly Li > >> Cc: Kent Overstreet > >> Cc: Ard Biesheuvel > >> Cc: linux-bcache@vger.kernel.org > >> --- > >> drivers/md/bcache/super.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c > >> index e42f1400cea9..a76ce92502ed 100644 > >> --- a/drivers/md/bcache/super.c > >> +++ b/drivers/md/bcache/super.c > >> @@ -546,7 +546,8 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid) > >> > >> static struct uuid_entry *uuid_find_empty(struct cache_set *c) > >> { > >> - static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"; > >> + static const char zero_uuid[] __nonstring = > > > > Hi Kees, > > > I notice zero_uuid[16] changes to zero_uuid[], then the element number information is removed. > > > > Is it OK for GCC 15 to only add __nonstring and keep zero_uuid[16]? Either way is fine. I can update the patch to use the "[16]" again if you'd like? -Kees > Ping ? > > You are expert here, I need your opinion. > > Thanks. > > Coly Li > > > > >> + { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; > >> > >> return uuid_find(c, zero_uuid); > >> } > >> -- > >> 2.34.1 > > -- Kees Cook