From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750820AbVHLSVq (ORCPT ); Fri, 12 Aug 2005 14:21:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750872AbVHLSVq (ORCPT ); Fri, 12 Aug 2005 14:21:46 -0400 Received: from mail-relay-1.tiscali.it ([213.205.33.41]:47821 "EHLO mail-relay-1.tiscali.it") by vger.kernel.org with ESMTP id S1750820AbVHLSPS (ORCPT ); Fri, 12 Aug 2005 14:15:18 -0400 Subject: [patch 18/39] remap_file_pages protection support: add VM_FAULT_SIGSEGV To: akpm@osdl.org Cc: jdike@addtoit.com, linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, blaisorblade@yahoo.it, mingo@elte.hu From: blaisorblade@yahoo.it Date: Fri, 12 Aug 2005 20:21:45 +0200 Message-Id: <20050812182145.DF52E24E7F3@zion.home.lan> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Ingo Molnar Since with remap_file_pages w/prot we may put PROT_NONE on a single PTE rather than a VMA, we must handle that inside handle_mm_fault. This value must be handled in the arch-specific fault handlers, and this change must be ported to every arch on the world; now the new support is not in a separate syscall, so this *must* be done unless we want stability / security issues (the *BUG()* for unknown return values of handle_mm_fault() is triggerable from userspace calling remap_file_pages, and on other archs, we have VM_FAULT_OOM which is worse). However, I've alleviated this need via the previous "safety net" patch. This patch includes the arch-specific part for i386. Note, however, that _proper_ support is more intrusive; we can allow a write on a readonly VMA, but the arch fault handler currently stops that; it should test VM_NONUNIFORM instead and call handle_mm_fault() in case it's set. And it will have to do on its own all protection checks. This is in the following patches. Signed-off-by: Paolo 'Blaisorblade' Giarrusso --- linux-2.6.git-paolo/arch/i386/mm/fault.c | 2 ++ linux-2.6.git-paolo/include/linux/mm.h | 9 +++++---- linux-2.6.git-paolo/mm/memory.c | 12 ++++++++++++ 3 files changed, 19 insertions(+), 4 deletions(-) diff -puN arch/i386/mm/fault.c~rfp-add-vm_fault_sigsegv arch/i386/mm/fault.c --- linux-2.6.git/arch/i386/mm/fault.c~rfp-add-vm_fault_sigsegv 2005-08-11 14:19:57.000000000 +0200 +++ linux-2.6.git-paolo/arch/i386/mm/fault.c 2005-08-11 14:19:58.000000000 +0200 @@ -351,6 +351,8 @@ good_area: goto do_sigbus; case VM_FAULT_OOM: goto out_of_memory; + case VM_FAULT_SIGSEGV: + goto bad_area; default: BUG(); } diff -puN include/linux/mm.h~rfp-add-vm_fault_sigsegv include/linux/mm.h --- linux-2.6.git/include/linux/mm.h~rfp-add-vm_fault_sigsegv 2005-08-11 14:19:58.000000000 +0200 +++ linux-2.6.git-paolo/include/linux/mm.h 2005-08-11 14:19:58.000000000 +0200 @@ -632,10 +632,11 @@ static inline int page_mapped(struct pag * Used to decide whether a process gets delivered SIGBUS or * just gets major/minor fault counters bumped up. */ -#define VM_FAULT_OOM (-1) -#define VM_FAULT_SIGBUS 0 -#define VM_FAULT_MINOR 1 -#define VM_FAULT_MAJOR 2 +#define VM_FAULT_OOM (-1) +#define VM_FAULT_SIGBUS 0 +#define VM_FAULT_MINOR 1 +#define VM_FAULT_MAJOR 2 +#define VM_FAULT_SIGSEGV 3 #define offset_in_page(p) ((unsigned long)(p) & ~PAGE_MASK) diff -puN mm/memory.c~rfp-add-vm_fault_sigsegv mm/memory.c --- linux-2.6.git/mm/memory.c~rfp-add-vm_fault_sigsegv 2005-08-11 14:19:58.000000000 +0200 +++ linux-2.6.git-paolo/mm/memory.c 2005-08-11 14:19:58.000000000 +0200 @@ -1995,6 +1995,18 @@ static inline int handle_pte_fault(struc return do_swap_page(mm, vma, address, pte, pmd, entry, write_access); } + /* + * Generate a SIGSEGV if a PROT_NONE page is accessed; this is handled + * in arch-specific code if the whole VMA has PROT_NONE, and here if + * just this pte has PROT_NONE (which can be done only with + * remap_file_pages). + */ + if (pgprot_val(pte_to_pgprot(entry)) == pgprot_val(__P000)) { + pte_unmap(pte); + spin_unlock(&mm->page_table_lock); + return VM_FAULT_SIGSEGV; + } + if (write_access) { if (!pte_write(entry)) return do_wp_page(mm, vma, address, pte, pmd, entry); _