From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757434AbdJKPkO (ORCPT ); Wed, 11 Oct 2017 11:40:14 -0400 Received: from mail-it0-f45.google.com ([209.85.214.45]:57052 "EHLO mail-it0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757254AbdJKPkM (ORCPT ); Wed, 11 Oct 2017 11:40:12 -0400 X-Google-Smtp-Source: AOwi7QCBFaMzYQURZjWPVIlupX0pZEfJ9647HLzIqZlD1Y3hLngTU8fXwvCSOTrwg61zuPxkyOtoFA== From: Tycho Andersen To: Kees Cook Cc: linux-kernel@vger.kernel.org, Tycho Andersen , Andy Lutomirski , Oleg Nesterov Subject: [PATCH v3 1/2] seccomp: hoist out filter resolving logic Date: Wed, 11 Oct 2017 09:39:20 -0600 Message-Id: <20171011153921.20731-1-tycho@docker.com> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hoist out the nth filter resolving logic that ptrace uses into a new function. We'll use this in the next patch to implement the new PTRACE_SECCOMP_GET_FILTER_FLAGS command. v3: * significantly revamp get_nth_filter logic (Oleg) * rebase on 4.14-rc4, using the new __{get,put}_seccomp_filter primitives Signed-off-by: Tycho Andersen CC: Kees Cook CC: Andy Lutomirski CC: Oleg Nesterov --- kernel/seccomp.c | 77 +++++++++++++++++++++++++++++++++----------------------- 1 file changed, 45 insertions(+), 32 deletions(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index bb3a38005b9c..2e1568261ac4 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -977,49 +977,68 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) } #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) -long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, - void __user *data) +static struct seccomp_filter *get_nth_filter(struct task_struct *task, + unsigned long filter_off) { - struct seccomp_filter *filter; - struct sock_fprog_kern *fprog; - long ret; - unsigned long count = 0; - - if (!capable(CAP_SYS_ADMIN) || - current->seccomp.mode != SECCOMP_MODE_DISABLED) { - return -EACCES; - } + struct seccomp_filter *orig, *filter; + unsigned long count; + /* + * Note: this is only correct because the caller should be the (ptrace) + * tracer of the task, otherwise lock_task_sighand is needed. + */ spin_lock_irq(&task->sighand->siglock); + if (task->seccomp.mode != SECCOMP_MODE_FILTER) { - ret = -EINVAL; - goto out; + spin_unlock_irq(&task->sighand->siglock); + return ERR_PTR(-EINVAL); } - filter = task->seccomp.filter; - while (filter) { - filter = filter->prev; + orig = task->seccomp.filter; + __get_seccomp_filter(orig); + spin_unlock_irq(&task->sighand->siglock); + + count = 0; + for (filter = orig; filter; filter = filter->prev) count++; - } if (filter_off >= count) { - ret = -ENOENT; + filter = ERR_PTR(-ENOENT); goto out; } - count -= filter_off; - filter = task->seccomp.filter; - while (filter && count > 1) { - filter = filter->prev; + count -= filter_off; + for (filter = orig; filter && count > 1; filter = filter->prev) count--; - } if (WARN_ON(count != 1 || !filter)) { - /* The filter tree shouldn't shrink while we're using it. */ - ret = -ENOENT; + filter = ERR_PTR(-ENOENT); goto out; } + __get_seccomp_filter(filter); + +out: + __put_seccomp_filter(orig); + return filter; +} + +long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, + void __user *data) +{ + struct seccomp_filter *filter; + struct sock_fprog_kern *fprog; + long ret; + + if (!capable(CAP_SYS_ADMIN) || + current->seccomp.mode != SECCOMP_MODE_DISABLED) { + return -EACCES; + } + + filter = get_nth_filter(task, filter_off); + if (IS_ERR(filter)) + return PTR_ERR(filter); + fprog = filter->prog->orig_prog; if (!fprog) { /* This must be a new non-cBPF filter, since we save @@ -1034,17 +1053,11 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, if (!data) goto out; - __get_seccomp_filter(filter); - spin_unlock_irq(&task->sighand->siglock); - if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) ret = -EFAULT; - __put_seccomp_filter(filter); - return ret; - out: - spin_unlock_irq(&task->sighand->siglock); + __put_seccomp_filter(filter); return ret; } #endif -- 2.11.0