From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751352AbeBTUMf (ORCPT ); Tue, 20 Feb 2018 15:12:35 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:40554 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751245AbeBTUMe (ORCPT ); Tue, 20 Feb 2018 15:12:34 -0500 Date: Tue, 20 Feb 2018 21:13:28 +0100 From: Eugene Syromiatnikov To: Tycho Andersen 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: <20180220201328.GR4439@asgard.redhat.com> References: <20171115020019.13517-1-tycho@tycho.ws> <20171115020019.13517-2-tycho@tycho.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171115020019.13517-2-tycho@tycho.ws> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > + > + 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? > + if (filter->log) > + kmd.flags |= SECCOMP_FILTER_FLAG_LOG; > + > + ret = size; > + if (copy_to_user(data, &kmd, size)) > + ret = -EFAULT; > + > + __put_seccomp_filter(filter); > + return ret; > + > +} > #endif > > #ifdef CONFIG_SYSCTL > -- > 2.14.1 >