From: Paulo Alcantara <pc@cjr•nz>
To: Kees Cook <keescook@chromium•org>,
"Eric W. Biederman" <ebiederm@xmission•com>
Cc: "Kees Cook" <keescook@chromium•org>,
"David Howells" <dhowells@redhat•com>,
"Luis Chamberlain" <mcgrof@kernel•org>,
"Russ Weight" <russell.h.weight@intel•com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation•org>,
"Rafael J. Wysocki" <rafael@kernel•org>,
"Steve French" <sfrench@samba•org>,
"Ronnie Sahlberg" <lsahlber@redhat•com>,
"Shyam Prasad N" <sprasad@microsoft•com>,
"Tom Talpey" <tom@talpey•com>,
"Namjae Jeon" <linkinjeon@kernel•org>,
"Sergey Senozhatsky" <senozhatsky@chromium•org>,
"Trond Myklebust" <trond.myklebust@hammerspace•com>,
"Anna Schumaker" <anna@kernel•org>,
"Chuck Lever" <chuck.lever@oracle•com>,
"Jeff Layton" <jlayton@kernel•org>,
"David S. Miller" <davem@davemloft•net>,
"Eric Dumazet" <edumazet@google•com>,
"Jakub Kicinski" <kuba@kernel•org>,
"Paolo Abeni" <pabeni@redhat•com>,
"Michal Koutný" <mkoutny@suse•com>,
"Peter Zijlstra" <peterz@infradead•org>,
linux-cifs@vger•kernel.org, samba-technical@lists•samba.org,
linux-nfs@vger•kernel.org, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org, linux-hardening@vger•kernel.org
Subject: Re: [PATCH] cred: Do not default to init_cred in prepare_kernel_cred()
Date: Thu, 27 Oct 2022 09:03:08 -0300 [thread overview]
Message-ID: <87bkpxh3sz.fsf@cjr.nz> (raw)
In-Reply-To: <20221026232943.never.775-kees@kernel.org>
Kees Cook <keescook@chromium•org> writes:
> A common exploit pattern for ROP attacks is to abuse prepare_kernel_cred()
> in order to construct escalated privileges[1]. Instead of providing a
> short-hand argument (NULL) to the "daemon" argument to indicate using
> init_cred as the base cred, require that "daemon" is always set to
> an actual task. Replace all existing callers that were passing NULL
> with &init_task.
>
> Future attacks will need to have sufficiently powerful read/write
> primitives to have found an appropriately privileged task and written it
> to the ROP stack as an argument to succeed, which is similarly difficult
> to the prior effort needed to escalate privileges before struct cred
> existed: locate the current cred and overwrite the uid member.
>
> This has the added benefit of meaning that prepare_kernel_cred() can no
> longer exceed the privileges of the init task, which may have changed from
> the original init_cred (e.g. dropping capabilities from the bounding set).
>
> [1] https://google.com/search?q=commit_creds(prepare_kernel_cred(0))
>
> Cc: "Eric W. Biederman" <ebiederm@xmission•com>
> Cc: David Howells <dhowells@redhat•com>
> Cc: Luis Chamberlain <mcgrof@kernel•org>
> Cc: Russ Weight <russell.h.weight@intel•com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation•org>
> Cc: "Rafael J. Wysocki" <rafael@kernel•org>
> Cc: Steve French <sfrench@samba•org>
> Cc: Paulo Alcantara <pc@cjr•nz>
> Cc: Ronnie Sahlberg <lsahlber@redhat•com>
> Cc: Shyam Prasad N <sprasad@microsoft•com>
> Cc: Tom Talpey <tom@talpey•com>
> Cc: Namjae Jeon <linkinjeon@kernel•org>
> Cc: Sergey Senozhatsky <senozhatsky@chromium•org>
> Cc: Trond Myklebust <trond.myklebust@hammerspace•com>
> Cc: Anna Schumaker <anna@kernel•org>
> Cc: Chuck Lever <chuck.lever@oracle•com>
> Cc: Jeff Layton <jlayton@kernel•org>
> Cc: "David S. Miller" <davem@davemloft•net>
> Cc: Eric Dumazet <edumazet@google•com>
> Cc: Jakub Kicinski <kuba@kernel•org>
> Cc: Paolo Abeni <pabeni@redhat•com>
> Cc: "Michal Koutný" <mkoutny@suse•com>
> Cc: Peter Zijlstra <peterz@infradead•org>
> Cc: linux-cifs@vger•kernel.org
> Cc: samba-technical@lists•samba.org
> Cc: linux-nfs@vger•kernel.org
> Cc: netdev@vger•kernel.org
> Signed-off-by: Kees Cook <keescook@chromium•org>
> ---
> drivers/base/firmware_loader/main.c | 2 +-
> fs/cifs/cifs_spnego.c | 2 +-
> fs/cifs/cifsacl.c | 2 +-
> fs/ksmbd/smb_common.c | 2 +-
> fs/nfs/flexfilelayout/flexfilelayout.c | 4 ++--
> fs/nfs/nfs4idmap.c | 2 +-
> fs/nfsd/nfs4callback.c | 2 +-
> kernel/cred.c | 15 +++++++--------
> net/dns_resolver/dns_key.c | 2 +-
> 9 files changed, 16 insertions(+), 17 deletions(-)
Acked-by: Paulo Alcantara (SUSE) <pc@cjr•nz>
next prev parent reply other threads:[~2022-10-27 12:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-26 23:31 [PATCH] cred: Do not default to init_cred in prepare_kernel_cred() Kees Cook
2022-10-27 6:49 ` Greg Kroah-Hartman
2022-10-27 12:03 ` Paulo Alcantara [this message]
2022-10-27 13:07 ` Sergey Senozhatsky
2022-10-27 17:03 ` Luis Chamberlain
2022-10-27 17:16 ` Russ Weight
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