From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D72A32D9EFB; Fri, 31 Jul 2026 09:17:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785489422; cv=none; b=HE2MjIfpIrZQaU8MMe2OZmuxaTh/JA/vETFCAwLcFMhLAS37w/SCp8JnkONCk5TcHquIxsg5TfHjkOqI0t3FwhDziCfopWo7lzWbSQb9zYEKx++zrDihTW+06J7ZA4SKIc23/S0ue6uLYM8xDi/GBXqIqfQWmqSa0gWUXukbOrU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785489422; c=relaxed/simple; bh=STdaIP3BkiVmPg2LzJMfTZnSTYZgh/uiXsJvPKHCoG0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Sc8fXku1w2KdbydUCRBk10fIsBLMhgMTX2hM/zIb5QScGVK34oMQig8BtR44khI3Kf8yTWWM0kcFv9xa5ol/RZ/7XMOgjPsNsOalRRsNNO/asuesNHZcox0qUb357ZvXYCvCg3oCoN24ljPRAXBKGyPp0Yi9vgKK5tfJp6Rc9z4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hVqZv+eN; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hVqZv+eN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A682E1F000E9; Fri, 31 Jul 2026 09:16:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785489420; bh=lUJhtLi6sjw4TDrdtAdIGO4QqwN3Ldi1q7BaQU8Zx0g=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hVqZv+eNQ0zmamVWG/pRAGaYY20PIzxTUffAL7k+7erCUTDQ3iIWfWrFI+Oc9rF6S 5WGp/o28iCUUc5xqTUHdmi4Wu/G7YuvjFbYzn1/y9IAdFsv+fdkl38lrwI5dsIzZfX O3aDueXRG0pkUQ33hAmi/+n7v//J67j6pbrbIOI2hdwmMfzWCfTPa1yQxVcQ7vQ7Cp vEI7DoV0xD1td3+Hhhp0EZopRrqN0Hx8iNzGT+pbgXY1YFtQrYBoc3laNWv5JO87Bi HY9N/yQ/Qos2JjrIJyPT1nPDMW5wnrfyHB1qeF3OtB7t+S6vyx/cQWy3Qp78GkR8AJ vauF1M+uhhwDA== Message-ID: <3bf1002b-4e3e-4670-a3d9-2f5b7f67beb7@kernel.org> Date: Fri, 31 Jul 2026 11:16:57 +0200 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] tty: vcc: zero-initialize control packet in vcc_send_ctl() To: Greg Kroah-Hartman Cc: sparclinux@vger.kernel.org, "David S. Miller" , Joshua Rogers , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, stable , Kees Cook References: <20260731-aisle-tty-vcc-v1-0-962e18beb8a8@linuxfoundation.org> <20260731-aisle-tty-vcc-v1-1-962e18beb8a8@linuxfoundation.org> <42534bff-4aed-497d-bb9c-e413b92493cb@kernel.org> <2026073155-leverage-rentable-fbbd@gregkh> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; keydata= xsFNBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABzSFKaXJpIFNsYWJ5 IDxqaXJpc2xhYnlAa2VybmVsLm9yZz7CwXcEEwEIACEFAlW3RUwCGwMFCwkIBwIGFQgJCgsC BBYCAwECHgECF4AACgkQvSWxBAa0cEnVTg//TQpdIAr8Tn0VAeUjdVIH9XCFw+cPSU+zMSCH eCZoA/N6gitEcnvHoFVVM7b3hK2HgoFUNbmYC0RdcSc80pOF5gCnACSP9XWHGWzeKCARRcQR 4s5YD8I4VV5hqXcKo2DFAtIOVbHDW+0okOzcecdasCakUTr7s2fXz97uuoc2gIBB7bmHUGAH XQXHvdnCLjDjR+eJN+zrtbqZKYSfj89s/ZHn5Slug6w8qOPT1sVNGG+eWPlc5s7XYhT9z66E l5C0rG35JE4PhC+tl7BaE5IwjJlBMHf/cMJxNHAYoQ1hWQCKOfMDQ6bsEr++kGUCbHkrEFwD UVA72iLnnnlZCMevwE4hc0zVhseWhPc/KMYObU1sDGqaCesRLkE3tiE7X2cikmj/qH0CoMWe gjnwnQ2qVJcaPSzJ4QITvchEQ+tbuVAyvn9H+9MkdT7b7b2OaqYsUP8rn/2k1Td5zknUz7iF oJ0Z9wPTl6tDfF8phaMIPISYrhceVOIoL+rWfaikhBulZTIT5ihieY9nQOw6vhOfWkYvv0Dl o4GRnb2ybPQpfEs7WtetOsUgiUbfljTgILFw3CsPW8JESOGQc0Pv8ieznIighqPPFz9g+zSu Ss/rpcsqag5n9rQp/H3WW5zKUpeYcKGaPDp/vSUovMcjp8USIhzBBrmI7UWAtuedG9prjqfO wU0ETpLnhgEQAM+cDWLL+Wvc9cLhA2OXZ/gMmu7NbYKjfth1UyOuBd5emIO+d4RfFM02XFTI t4MxwhAryhsKQQcA4iQNldkbyeviYrPKWjLTjRXT5cD2lpWzr+Jx7mX7InV5JOz1Qq+P+nJW YIBjUKhI03ux89p58CYil24Zpyn2F5cX7U+inY8lJIBwLPBnc9Z0An/DVnUOD+0wIcYVnZAK DiIXODkGqTg3fhZwbbi+KAhtHPFM2fGw2VTUf62IHzV+eBSnamzPOBc1XsJYKRo3FHNeLuS8 f4wUe7bWb9O66PPFK/RkeqNX6akkFBf9VfrZ1rTEKAyJ2uqf1EI1olYnENk4+00IBa+BavGQ 8UW9dGW3nbPrfuOV5UUvbnsSQwj67pSdrBQqilr5N/5H9z7VCDQ0dhuJNtvDSlTf2iUFBqgk 3smln31PUYiVPrMP0V4ja0i9qtO/TB01rTfTyXTRtqz53qO5dGsYiliJO5aUmh8swVpotgK4 /57h3zGsaXO9PGgnnAdqeKVITaFTLY1ISg+Ptb4KoliiOjrBMmQUSJVtkUXMrCMCeuPDGHo7 39Xc75lcHlGuM3yEB//htKjyprbLeLf1y4xPyTeeF5zg/0ztRZNKZicgEmxyUNBHHnBKHQxz 1j+mzH0HjZZtXjGu2KLJ18G07q0fpz2ZPk2D53Ww39VNI/J9ABEBAAHCwV8EGAECAAkFAk6S 54YCGwwACgkQvSWxBAa0cEk3tRAAgO+DFpbyIa4RlnfpcW17AfnpZi9VR5+zr496n2jH/1ld wRO/S+QNSA8qdABqMb9WI4BNaoANgcg0AS429Mq0taaWKkAjkkGAT7mD1Q5PiLr06Y/+Kzdr 90eUVneqM2TUQQbK+Kh7JwmGVrRGNqQrDk+gRNvKnGwFNeTkTKtJ0P8jYd7P1gZb9Fwj9YLx jhn/sVIhNmEBLBoI7PL+9fbILqJPHgAwW35rpnq4f/EYTykbk1sa13Tav6btJ+4QOgbcezWI wZ5w/JVfEJW9JXp3BFAVzRQ5nVrrLDAJZ8Y5ioWcm99JtSIIxXxt9FJaGc1Bgsi5K/+dyTKL wLMJgiBzbVx8G+fCJJ9YtlNOPWhbKPlrQ8+AY52Aagi9WNhe6XfJdh5g6ptiOILm330mkR4g W6nEgZVyIyTq3ekOuruftWL99qpP5zi+eNrMmLRQx9iecDNgFr342R9bTDlb1TLuRb+/tJ98 f/bIWIr0cqQmqQ33FgRhrG1+Xml6UXyJ2jExmlO8JljuOGeXYh6ZkIEyzqzffzBLXZCujlYQ DFXpyMNVJ2ZwPmX2mWEoYuaBU0JN7wM+/zWgOf2zRwhEuD3A2cO2PxoiIfyUEfB9SSmffaK/ S4xXoB6wvGENZ85Hg37C7WDNdaAt6Xh2uQIly5grkgvWppkNy4ZHxE+jeNsU7tg= In-Reply-To: <2026073155-leverage-rentable-fbbd@gregkh> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 31. 07. 26, 10:32, Greg Kroah-Hartman wrote: > On Fri, Jul 31, 2026 at 10:29:14AM +0200, Jiri Slaby wrote: >> On 31. 07. 26, 10:15, Greg Kroah-Hartman wrote: >>> From: Joshua Rogers >>> >>> The stack-allocated struct vio_vcc pkt was partially initialized, >>> leaving the tag.stype_env field uninitialized before being sent via >>> ldc_write(), potentially leaking kernel stack data to the LDC peer. >>> >>> Assisted-by: AISLE:Snapshot >>> Cc: stable >>> Signed-off-by: Joshua Rogers >>> Signed-off-by: Greg Kroah-Hartman >>> --- >>> drivers/tty/vcc.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/tty/vcc.c b/drivers/tty/vcc.c >>> index 27a55465bf5e..3947bd2b75ac 100644 >>> --- a/drivers/tty/vcc.c >>> +++ b/drivers/tty/vcc.c >>> @@ -492,7 +492,7 @@ static ssize_t domain_show(struct device *dev, >>> static int vcc_send_ctl(struct vcc_port *port, int ctl) >>> { >>> - struct vio_vcc pkt; >>> + struct vio_vcc pkt = {}; >> >> Note this needs not initialize holes. > > Does it? I keep forgetting this if it's really true or not. I think > we've been through this in the past but I can't find the archives. > >> I believe there are none here, but memset() is usually >> preferred/safer. > > Last I remember, a long time ago, the compiler would just use memset() > for this, and hit the holes. Or is that a compiler-specific issue? > > Yes, it's more obvious, and I'll be glad to change it, but figuring this > out for real would be great :) OK, so the standard (C17) does not guarantee zeroing. What I found though: * both clang and gcc zero the full struct for "{}". There was a bug in gcc < 8 where it did not. * this is not true for designated initializer, cf. ce50039be49e ("net: sched: act_ife: initialize struct tc_ife to fix KMSAN kernel-infoleak")). Adding Kees who is the author of: ==== Memory initialization --------------------- Memory copied to userspace must always be fully initialized. If not explicitly memset(), this will require changes to the compiler to make sure structure holes are cleared. ==== He might aware of more bugs. FWIW, {} here should be safe for two reasons: * not a designated initializer * no holes (IMO) thanks, -- js suse labs