Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759419Ab2BJOn7 (ORCPT ); Fri, 10 Feb 2012 09:43:59 -0500 Received: from mail-we0-f174.google.com ([74.125.82.174]:55014 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759406Ab2BJOn4 (ORCPT ); Fri, 10 Feb 2012 09:43:56 -0500 From: Denys Vlasenko To: Andrew Morton , Oleg Nesterov , Tejun Heo , Pedro Alves , Jan Kratochvil , linux-kernel@vger.kernel.org Cc: Denys Vlasenko Subject: [PATCH 3/5] ptrace: make PTRACE_SEIZE set ptrace options specified in 'data' parameter Date: Fri, 10 Feb 2012 15:43:09 +0100 Message-Id: <1328884991-23889-4-git-send-email-vda.linux@googlemail.com> X-Mailer: git-send-email 1.7.7.6 In-Reply-To: <1328884991-23889-3-git-send-email-vda.linux@googlemail.com> References: <1328884991-23889-1-git-send-email-vda.linux@googlemail.com> <1328884991-23889-2-git-send-email-vda.linux@googlemail.com> <1328884991-23889-3-git-send-email-vda.linux@googlemail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3703 Lines: 107 This can be used to close a few corner cases in strace where we get unwanted racy behavior after attach, but before we have a chance to set options (the notorious post-execve SIGTRAP comes to mind), and removes the need to track "did we set opts for this task" state in strace internals. While we are at it: Make it possible to extend SEIZE in the future with more functionality by passing non-zero 'addr' parameter. To that end, error out if 'addr' is non-zero. PTRACE_ATTACH did not (and still does not) have such check, and users (strace) do pass garbage there... let's avoid repeating this mistake with SEIZE. Set all task->ptrace bits in one operation - before this change, we were adding PT_SEIZED and PT_PTRACE_CAP with task->ptrace |= BIT ops. This was probably ok (not a bug), but let's be on a safer side. Changes since v2: use (unsigned long) casts instead of (long) ones, move PTRACE_SEIZE_DEVEL-related code to separate lines of code. Signed-off-by: Denys Vlasenko Acked-by: Tejun Heo --- kernel/ptrace.c | 29 ++++++++++++++++++++--------- 1 files changed, 20 insertions(+), 9 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 9acd07a..99a18a0 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -231,6 +231,7 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode) } static int ptrace_attach(struct task_struct *task, long request, + unsigned long addr, unsigned long flags) { bool seize = (request == PTRACE_SEIZE); @@ -238,19 +239,29 @@ static int ptrace_attach(struct task_struct *task, long request, /* * SEIZE will enable new ptrace behaviors which will be implemented - * gradually. SEIZE_DEVEL is used to prevent applications + * gradually. SEIZE_DEVEL bit is used to prevent applications * expecting full SEIZE behaviors trapping on kernel commits which * are still in the process of implementing them. * * Only test programs for new ptrace behaviors being implemented * should set SEIZE_DEVEL. If unset, SEIZE will fail with -EIO. * - * Once SEIZE behaviors are completely implemented, this flag and - * the following test will be removed. + * Once SEIZE behaviors are completely implemented, this flag + * will be removed. */ retval = -EIO; - if (seize && !(flags & PTRACE_SEIZE_DEVEL)) - goto out; + if (seize) { + if (addr != 0) + goto out; + if (!(flags & PTRACE_SEIZE_DEVEL)) + goto out; + flags &= ~(unsigned long)PTRACE_SEIZE_DEVEL; + if (flags & ~(unsigned long)PTRACE_O_MASK) + goto out; + flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT); + } else { + flags = PT_PTRACED; + } audit_ptrace(task); @@ -282,11 +293,11 @@ static int ptrace_attach(struct task_struct *task, long request, if (task->ptrace) goto unlock_tasklist; - task->ptrace = PT_PTRACED; if (seize) - task->ptrace |= PT_SEIZED; + flags |= PT_SEIZED; if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE)) - task->ptrace |= PT_PTRACE_CAP; + flags |= PT_PTRACE_CAP; + task->ptrace = flags; __ptrace_link(task, current); @@ -879,7 +890,7 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr, } if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) { - ret = ptrace_attach(child, request, data); + ret = ptrace_attach(child, request, addr, data); /* * Some architectures need to do book-keeping after * a ptrace attach. -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/