linux-hardening - Re: [PATCH] RDMA/uverbs: Remove flexible arrays from struct *

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date: Mon, 12 Feb 2024 14:59:56 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Kees Cook <keescook@...omium.org>
Cc: Erick Archer <erick.archer@....com>, Leon Romanovsky <leon@...nel.org>,
	Edward Srouji <edwards@...dia.com>,
	Patrisious Haddad <phaddad@...dia.com>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] RDMA/uverbs: Remove flexible arrays from struct *_filter

On Mon, Feb 12, 2024 at 10:30:17AM -0800, Kees Cook wrote:
> I might suggest doing a binary difference comparison[1], as it's possible
> that "real_sz" is being used to try to avoid trailing padding on
> structs. I wasn't able to trivially construct an example, so maybe I'm
> not understanding its purpose correctly.

Hmm.. No need for binary comparison:

+static_assert(offsetof(struct ib_flow_eth_filter, real_sz) == sizeof(struct ib_flow_eth_filter));
+static_assert(offsetof(struct ib_flow_ib_filter, real_sz) == sizeof(struct ib_flow_ib_filter));
+static_assert(offsetof(struct ib_flow_tunnel_filter, real_sz) == sizeof(struct ib_flow_tunnel_filter));
+static_assert(offsetof(struct ib_flow_esp_filter, real_sz) == sizeof(struct ib_flow_esp_filter));
+static_assert(offsetof(struct ib_flow_gre_filter, real_sz) == sizeof(struct ib_flow_gre_filter));
+static_assert(offsetof(struct ib_flow_mpls_filter, real_sz) == sizeof(struct ib_flow_mpls_filter));

But yep, it is doing something:

In file included from ../include/linux/mlx5/device.h:37:
../include/rdma/ib_verbs.h:1931:15: error: static assertion failed due to requirement '__builtin_offsetof(struct ib_flow_ib_filter, real_sz) == sizeof(struct ib_flow_ib_filter)': offsetof(struct ib_flow_ib_filter, real_sz) == sizeof(struct ib_flow_ib_filter)
 1931 | static_assert(offsetof(struct ib_flow_ib_filter, real_sz) == sizeof(struct ib_flow_ib_filter));

__packed on that struct would probably be be OK.

Jason