Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751791AbbGMMGw (ORCPT ); Mon, 13 Jul 2015 08:06:52 -0400 Received: from mail-wi0-f169.google.com ([209.85.212.169]:34825 "EHLO mail-wi0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750792AbbGMMGv (ORCPT ); Mon, 13 Jul 2015 08:06:51 -0400 MIME-Version: 1.0 X-Originating-IP: [212.25.79.130] In-Reply-To: <1436784852-144369-3-git-send-email-kirill.shutemov@linux.intel.com> References: <1436784852-144369-1-git-send-email-kirill.shutemov@linux.intel.com> <1436784852-144369-3-git-send-email-kirill.shutemov@linux.intel.com> From: Leon Romanovsky Date: Mon, 13 Jul 2015 15:06:30 +0300 Message-ID: Subject: Re: [PATCH 2/5] x86, mpx: do not set ->vm_ops on mpx VMAs To: "Kirill A. Shutemov" Cc: Andrew Morton , Oleg Nesterov , Linux-MM , "linux-kernel@vger.kernel.org" , Dave Hansen , Andy Lutomirski , Thomas Gleixner Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3999 Lines: 122 Hi Kirill, On Mon, Jul 13, 2015 at 1:54 PM, Kirill A. Shutemov wrote: > > MPX setups private anonymous mapping, but uses vma->vm_ops too. > This can confuse core VM, as it relies on vm->vm_ops to distinguish > file VMAs from anonymous. > > As result we will get SIGBUS, because handle_pte_fault() thinks it's > file VMA without vm_ops->fault and it doesn't know how to handle the > situation properly. > > Let's fix that by not setting ->vm_ops. > > We don't really need ->vm_ops here: MPX VMA can be detected with VM_MPX > flag. And vma_merge() will not merge MPX VMA with non-MPX VMA, because > ->vm_flags won't match. > > The only thing left is name of VMA. I'm not sure if it's part of ABI, or > we can just drop it. The patch keep it by providing arch_vma_name() on x86. > > Build tested only. > > Signed-off-by: Kirill A. Shutemov > Cc: Dave Hansen > Cc: Andy Lutomirski > Cc: Thomas Gleixner > --- > arch/x86/mm/mmap.c | 7 +++++++ > arch/x86/mm/mpx.c | 20 +------------------- > 2 files changed, 8 insertions(+), 19 deletions(-) > > diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c > index 9d518d693b4b..844b06d67df4 100644 > --- a/arch/x86/mm/mmap.c > +++ b/arch/x86/mm/mmap.c > @@ -126,3 +126,10 @@ void arch_pick_mmap_layout(struct mm_struct *mm) > mm->get_unmapped_area = arch_get_unmapped_area_topdown; > } > } > + > +const char *arch_vma_name(struct vm_area_struct *vma) > +{ > + if (vma->vm_flags & VM_MPX) > + return "[mpx]"; > + return NULL; > +} I sure that I'm missing something important. This function stores "[mpx]" string on this function stack and returns the pointer to that address. In current flow, this address is visible and accessible, however in can be a different in general case. > diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c > index c439ec478216..4d1c11c07fe1 100644 > --- a/arch/x86/mm/mpx.c > +++ b/arch/x86/mm/mpx.c > @@ -18,26 +18,9 @@ > #include > #include > > -static const char *mpx_mapping_name(struct vm_area_struct *vma) > -{ > - return "[mpx]"; > -} > - > -static struct vm_operations_struct mpx_vma_ops = { > - .name = mpx_mapping_name, > -}; > - > -static int is_mpx_vma(struct vm_area_struct *vma) > -{ > - return (vma->vm_ops == &mpx_vma_ops); > -} > - > /* > * This is really a simplified "vm_mmap". it only handles MPX > * bounds tables (the bounds directory is user-allocated). > - * > - * Later on, we use the vma->vm_ops to uniquely identify these > - * VMAs. > */ > static unsigned long mpx_mmap(unsigned long len) > { > @@ -83,7 +66,6 @@ static unsigned long mpx_mmap(unsigned long len) > ret = -ENOMEM; > goto out; > } > - vma->vm_ops = &mpx_vma_ops; > > if (vm_flags & VM_LOCKED) { > up_write(&mm->mmap_sem); > @@ -661,7 +643,7 @@ static int zap_bt_entries(struct mm_struct *mm, > * so stop immediately and return an error. This > * probably results in a SIGSEGV. > */ > - if (!is_mpx_vma(vma)) > + if (!(vma->vm_flags & VM_MPX)) > return -EINVAL; > > len = min(vma->vm_end, end) - addr; > -- > 2.1.4 > > -- > 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 -- Leon Romanovsky | Independent Linux Consultant www.leon.nu | leon@leon.nu -- 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/