From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f43.google.com (mail-wg0-f43.google.com [74.125.82.43]) by kanga.kvack.org (Postfix) with ESMTP id 003846B0069 for ; Fri, 24 Oct 2014 08:50:04 -0400 (EDT) Received: by mail-wg0-f43.google.com with SMTP id n12so996011wgh.2 for ; Fri, 24 Oct 2014 05:50:04 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id az9si1773850wib.86.2014.10.24.05.50.03 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Fri, 24 Oct 2014 05:50:03 -0700 (PDT) Date: Fri, 24 Oct 2014 14:49:53 +0200 (CEST) From: Thomas Gleixner Subject: Re: [PATCH v9 10/12] x86, mpx: add prctl commands PR_MPX_ENABLE_MANAGEMENT, PR_MPX_DISABLE_MANAGEMENT In-Reply-To: <1413088915-13428-11-git-send-email-qiaowei.ren@intel.com> Message-ID: References: <1413088915-13428-1-git-send-email-qiaowei.ren@intel.com> <1413088915-13428-11-git-send-email-qiaowei.ren@intel.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Qiaowei Ren Cc: "H. Peter Anvin" , Ingo Molnar , Dave Hansen , x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@linux-mips.org On Sun, 12 Oct 2014, Qiaowei Ren wrote: > +int mpx_enable_management(struct task_struct *tsk) > +{ > + struct mm_struct *mm = tsk->mm; > + void __user *bd_base = MPX_INVALID_BOUNDS_DIR; What's the point of initializing bd_base here. I had to look twice to figure out that it gets overwritten by task_get_bounds_dir() > @@ -285,6 +285,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) > struct xsave_struct *xsave_buf; > struct task_struct *tsk = current; > siginfo_t info; > + int ret = 0; > > prev_state = exception_enter(); > if (notify_die(DIE_TRAP, "bounds", regs, error_code, > @@ -312,8 +313,35 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) > */ > switch (status & MPX_BNDSTA_ERROR_CODE) { > case 2: /* Bound directory has invalid entry. */ > - if (do_mpx_bt_fault(xsave_buf)) > + down_write(¤t->mm->mmap_sem); The handling of mm->mmap_sem here is horrible. The only reason why you want to hold mmap_sem write locked in the first place is that you want to cover the allocation and the mm->bd_addr check. I think it's wrong to tie this to mmap_sem in the first place. If MPX is enabled then you should have mm->bd_addr and an explicit mutex to protect it. So the logic would look like this: mutex_lock(&mm->bd_mutex); if (!kernel_managed(mm)) do_trap(); else if (do_mpx_bt_fault()) force_sig(); mutex_unlock(&mm->bd_mutex); No tricks with mmap_sem, no special return value handling. Straight forward code instead of a convoluted and error prone mess. Hmm? Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org