From: Jakub Kicinski <kuba@kernel•org>
To: Kees Cook <kees@kernel•org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel•org>,
"David S. Miller" <davem@davemloft•net>,
Andrew Lunn <andrew@lunn•ch>,
"Kory Maincent (Dent Project)" <kory.maincent@bootlin•com>,
Michael Chan <michael.chan@broadcom•com>,
Andrew Lunn <andrew+netdev@lunn•ch>,
Eric Dumazet <edumazet@google•com>,
Paolo Abeni <pabeni@redhat•com>,
Potnuri Bharat Teja <bharat@chelsio•com>,
Christian Benvenuti <benve@cisco•com>,
Satish Kharat <satishkh@cisco•com>,
Manish Chopra <manishc@marvell•com>,
Simon Horman <horms@kernel•org>,
Edward Cree <ecree.xilinx@gmail•com>,
Przemek Kitszel <przemyslaw.kitszel@intel•com>,
Heiner Kallweit <hkallweit1@gmail•com>,
Ahmed Zaki <ahmed.zaki@intel•com>,
Rahul Rameshbabu <rrameshbabu@nvidia•com>,
Ido Schimmel <idosch@nvidia•com>,
Maxime Chevallier <maxime.chevallier@bootlin•com>,
Takeru Hayasaka <hayatake396@gmail•com>,
Jonathan Corbet <corbet@lwn•net>,
linux-kernel@vger•kernel.org, netdev@vger•kernel.org,
linux-hardening@vger•kernel.org
Subject: Re: [PATCH 3/3] UAPI: ethtool: Avoid flex-array in struct ethtool_link_settings
Date: Fri, 15 Nov 2024 13:50:58 -0800 [thread overview]
Message-ID: <20241115135058.01065c04@kernel.org> (raw)
In-Reply-To: <20241115204308.3821419-3-kees@kernel.org>
On Fri, 15 Nov 2024 12:43:05 -0800 Kees Cook wrote:
> struct ethtool_link_settings tends to be used as a header for other
> structures that have trailing bytes[1], but has a trailing flexible array
> itself. Using this overlapped with other structures leads to ambiguous
> object sizing in the compiler, so we want to avoid such situations (which
> have caused real bugs in the past). Detecting this can be done with
> -Wflex-array-member-not-at-end, which will need to be enabled globally.
>
> Using a tagged struct_group() to create a new ethtool_link_settings_hdr
> structure isn't possible as it seems we cannot use the tagged variant of
> struct_group() due to syntax issues from C++'s perspective (even within
> "extern C")[2]. Instead, we can just leave the offending member defined
> in UAPI and remove it from the kernel's view of the structure, as Linux
> doesn't actually use this member at all. There is also no change in
> size since it was already a flexible array that didn't contribute to
> size returned by any use of sizeof().
Perfect. I was starting to doubt if user space needs the member,
ethtool CLI doesn't but looks like NetworkManager does.
So as you say we'll cross that bridge...
Reviewed-by: Jakub Kicinski <kuba@kernel•org>
Thanks!
next prev parent reply other threads:[~2024-11-15 21:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-15 20:43 [PATCH 0/3] UAPI: ethtool: Avoid flex-array in struct ethtool_link_settings Kees Cook
2024-11-15 20:43 ` [PATCH 1/3] Revert "net: ethtool: Avoid thousands of -Wflex-array-member-not-at-end warnings" Kees Cook
2024-11-15 20:43 ` [PATCH 2/3] Revert "UAPI: ethtool: Use __struct_group() in struct ethtool_link_settings" Kees Cook
2024-11-15 20:43 ` [PATCH 3/3] UAPI: ethtool: Avoid flex-array in struct ethtool_link_settings Kees Cook
2024-11-15 21:50 ` Jakub Kicinski [this message]
2024-11-19 4:00 ` [PATCH 0/3] " patchwork-bot+netdevbpf
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