[0/1] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK

Message ID	1572967777-8812-1-git-send-email-rppt@linux.ibm.com (mailing list archive)
Headers	show Return-Path: <SRS0=wNtT=Y5=kvack.org=owner-linux-mm@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A9805214B2 Gateway: Authorized Use Only! Violators will be prosecuted for <linux-mm@kvack.org> from <rppt@linux.ibm.com>; Tue, 5 Nov 2019 15:29:47 -0000 Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 5 Nov 2019 15:29:41 -0000 From: Mike Rapoport <rppt@linux.ibm.com> To: linux-kernel@vger.kernel.org Cc: Andrea Arcangeli <aarcange@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, Daniel Colascione <dancol@google.com>, Jann Horn <jannh@google.com>, Linus Torvalds <torvalds@linux-foundation.org>, Lokesh Gidra <lokeshgidra@google.com>, Nick Kralevich <nnk@google.com>, Nosh Minwalla <nosh@google.com>, Pavel Emelyanov <ovzxemul@gmail.com>, Tim Murray <timmurray@google.com>, linux-api@vger.kernel.org, linux-mm@kvack.org, Mike Rapoport <rppt@linux.ibm.com> Subject: [PATCH 0/1] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK Date: Tue, 5 Nov 2019 17:29:36 +0200 Message-Id: <1572967777-8812-1-git-send-email-rppt@linux.ibm.com> Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK \| expand [0/1] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK [1/1] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK

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1572967777-8812-1-git-send-email-rppt@linux.ibm.com (mailing list archive)

Headers

DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A9805214B2
From: Mike Rapoport <rppt@linux.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Daniel Colascione <dancol@google.com>, Jann Horn <jannh@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Lokesh Gidra <lokeshgidra@google.com>,
 Nick Kralevich <nnk@google.com>,
        Nosh Minwalla <nosh@google.com>, Pavel Emelyanov <ovzxemul@gmail.com>,
        Tim Murray <timmurray@google.com>, linux-api@vger.kernel.org,
        linux-mm@kvack.org, Mike Rapoport <rppt@linux.ibm.com>
Subject: [PATCH 0/1] userfaultfd: require CAP_SYS_PTRACE for
 UFFD_FEATURE_EVENT_FORK
Date: Tue,  5 Nov 2019 17:29:36 +0200
Message-Id: <1572967777-8812-1-git-send-email-rppt@linux.ibm.com>
Sender: owner-linux-mm@kvack.org
Precedence: bulk

Series

userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK | expand

Message

Mike Rapoport Nov. 5, 2019, 3:29 p.m. UTC

Hi,

A while ago Andy noticed [1] that UFFD_FEATURE_EVENT_FORK used by an
unprivileged user may have security implications.

As the first step of the solution the following patch limits the
availably of UFFD_FEATURE_EVENT_FORK only for those having CAP_SYS_PTRACE.

The usage of CAP_SYS_PTRACE ensures compatibility with CRIU.

Yet, if there are other users of non-cooperative userfaultfd that run
without CAP_SYS_PTRACE, they would be broken :(

[1] https://lore.kernel.org/lkml/CALCETrWY+5ynDct7eU_nDUqx=okQvjm=Y5wJvA4ahBja=CQXGw@mail.gmail.com

Mike Rapoport (1):
  userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK

 fs/userfaultfd.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)