From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751549AbeBUCu2 (ORCPT ); Tue, 20 Feb 2018 21:50:28 -0500 Received: from mail-pl0-f65.google.com ([209.85.160.65]:43814 "EHLO mail-pl0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751408AbeBUCu0 (ORCPT ); Tue, 20 Feb 2018 21:50:26 -0500 X-Google-Smtp-Source: AH8x227ip7YxQdtrIz5YkiASNbsbhufFnvegrgXlXwR1BLqPHpmd2doeQXF+T8jd+dM88A9f2vvpfw== Date: Tue, 20 Feb 2018 19:50:22 -0700 From: Tycho Andersen To: Eugene Syromiatnikov Cc: Kees Cook , linux-kernel@vger.kernel.org, Andy Lutomirski , Oleg Nesterov Subject: Re: [PATCH v4 2/2] ptrace, seccomp: add support for retrieving seccomp metadata Message-ID: <20180221025022.nd5yjgrvl4dbfwv5@cisco> References: <20171115020019.13517-1-tycho@tycho.ws> <20171115020019.13517-2-tycho@tycho.ws> <20180220201328.GR4439@asgard.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180220201328.GR4439@asgard.redhat.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 20, 2018 at 09:13:28PM +0100, Eugene Syromiatnikov wrote: > On Tue, Nov 14, 2017 at 07:00:19PM -0700, Tycho Andersen wrote: > > With the new SECCOMP_FILTER_FLAG_LOG, we need to be able to extract these > > flags for checkpoint restore, since they describe the state of a filter. > > > > So, let's add PTRACE_SECCOMP_GET_METADATA, similar to ..._GET_FILTER, which > > returns the metadata of the nth filter (right now, just the flags). > > Hopefully this will be future proof, and new per-filter metadata can be > > added to this struct. > > > > v3: * use GET_METADATA instead of GET_FLAGS > > v4: * resend > > > > Signed-off-by: Tycho Andersen > > CC: Kees Cook > > CC: Andy Lutomirski > > CC: Oleg Nesterov > > --- > > include/linux/seccomp.h | 8 ++++++++ > > include/uapi/linux/ptrace.h | 6 ++++++ > > kernel/ptrace.c | 4 ++++ > > kernel/seccomp.c | 34 ++++++++++++++++++++++++++++++++++ > > 4 files changed, 52 insertions(+) > > > > diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h > > index 10f25f7e4304..c723a5c4e3ff 100644 > > --- a/include/linux/seccomp.h > > +++ b/include/linux/seccomp.h > > @@ -95,11 +95,19 @@ static inline void get_seccomp_filter(struct task_struct *tsk) > > #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) > > extern long seccomp_get_filter(struct task_struct *task, > > unsigned long filter_off, void __user *data); > > +extern long seccomp_get_metadata(struct task_struct *task, > > + unsigned long filter_off, void __user *data); > > #else > > static inline long seccomp_get_filter(struct task_struct *task, > > unsigned long n, void __user *data) > > { > > return -EINVAL; > > } > > +static inline long seccomp_get_metadata(struct task_struct *task, > > + unsigned long filter_off, > > + void __user *data) > > +{ > > + return -EINVAL; > > +} > > #endif /* CONFIG_SECCOMP_FILTER && CONFIG_CHECKPOINT_RESTORE */ > > #endif /* _LINUX_SECCOMP_H */ > > diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h > > index e3939e00980b..e46d82b91166 100644 > > --- a/include/uapi/linux/ptrace.h > > +++ b/include/uapi/linux/ptrace.h > > @@ -66,6 +66,12 @@ struct ptrace_peeksiginfo_args { > > #define PTRACE_SETSIGMASK 0x420b > > > > #define PTRACE_SECCOMP_GET_FILTER 0x420c > > +#define PTRACE_SECCOMP_GET_METADATA 0x420d > > + > > +struct seccomp_metadata { > > + unsigned long filter_off; /* Input: which filter */ > > + unsigned int flags; /* Output: filter's flags */ > > +}; > > > > /* Read signals from a shared (process wide) queue */ > > #define PTRACE_PEEKSIGINFO_SHARED (1 << 0) > > diff --git a/kernel/ptrace.c b/kernel/ptrace.c > > index 84b1367935e4..58291e9f3276 100644 > > --- a/kernel/ptrace.c > > +++ b/kernel/ptrace.c > > @@ -1092,6 +1092,10 @@ int ptrace_request(struct task_struct *child, long request, > > ret = seccomp_get_filter(child, addr, datavp); > > break; > > > > + case PTRACE_SECCOMP_GET_METADATA: > > + ret = seccomp_get_metadata(child, addr, datavp); > > + break; > > + > > default: > > break; > > } > > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > > index bad457862ee0..7f1f2f3ea549 100644 > > --- a/kernel/seccomp.c > > +++ b/kernel/seccomp.c > > @@ -1061,6 +1061,40 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, > > __put_seccomp_filter(filter); > > return ret; > > } > > + > > +long seccomp_get_metadata(struct task_struct *task, > > + unsigned long size, void __user *data) > > +{ > > + long ret; > > + struct seccomp_filter *filter; > > + struct seccomp_metadata kmd = {}; > > + > > + if (!capable(CAP_SYS_ADMIN) || > > + current->seccomp.mode != SECCOMP_MODE_DISABLED) { > > + return -EACCES; > > + } > > + > > > + size = min_t(unsigned long, size, sizeof(kmd)); > > + > > + if (copy_from_user(&kmd, data, size)) > > + return -EFAULT; > > This will work kinda funny if size is less than sizeof(kmd.filter_off). > And I see no reason for copying the whole structure when only filter_off > is needed. Yes, agreed. EINVAL seems better. > > + > > + filter = get_nth_filter(task, kmd.filter_off); > > + if (IS_ERR(filter)) > > + return PTR_ERR(filter); > > + > > + memset(&kmd, 0, sizeof(kmd)); > > Is rewriting the filter_off field to 0 intentional? It "shouldn't" matter, but it's probably better not to; I've fixed it in https://lkml.org/lkml/2018/2/20/755 Thanks! Tycho