netdev - Re: [PATCH net] net: nexthop: Initialize all fields in dumped nexthops

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <CANn89iLvqJXmCktm=8WoSuSWOAVHe35fy+WHet-U+psMW2gAoQ@mail.gmail.com>
Date: Tue, 23 Jul 2024 19:26:40 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Petr Machata <petrm@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	David Ahern <dsahern@...nel.org>, mlxsw@...dia.com, Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH net] net: nexthop: Initialize all fields in dumped nexthops

On Tue, Jul 23, 2024 at 6:50 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Jul 23, 2024 at 6:05 PM Petr Machata <petrm@...dia.com> wrote:
> >
> > struct nexthop_grp contains two reserved fields that are not initialized by
> > nla_put_nh_group(), and carry garbage. This can be observed e.g. with
> > strace (edited for clarity):
> >
> >     # ip nexthop add id 1 dev lo
> >     # ip nexthop add id 101 group 1
> >     # strace -e recvmsg ip nexthop get id 101
> >     ...
> >     recvmsg(... [{nla_len=12, nla_type=NHA_GROUP},
> >                  [{id=1, weight=0, resvd1=0x69, resvd2=0x67}]] ...) = 52
> >
> > The fields are reserved and therefore not currently used. But as they are, they
> > leak kernel memory, and the fact they are not just zero complicates repurposing
> > of the fields for new ends. Initialize the full structure.
> >
> > Fixes: 430a049190de ("nexthop: Add support for nexthop groups")
> > Signed-off-by: Petr Machata <petrm@...dia.com>
> > Reviewed-by: Ido Schimmel <idosch@...dia.com>
>
> Interesting... not sure why syzbot did not catch this one.
>
> Reviewed-by: Eric Dumazet <edumazet@...gle.com>

Hmmm... Do we have the guarantee that the compiler initializes padding ?

AFAIK, padding at the end of the structure is not initialized.