From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753861Ab1AEXsN (ORCPT ); Wed, 5 Jan 2011 18:48:13 -0500 Received: from kroah.org ([198.145.64.141]:41048 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753644Ab1AEXpQ (ORCPT ); Wed, 5 Jan 2011 18:45:16 -0500 X-Mailbox-Line: From gregkh@clark.site Wed Jan 5 15:03:27 2011 Message-Id: <20110105230327.076718056@clark.site> User-Agent: quilt/0.48-11.2 Date: Wed, 05 Jan 2011 15:00:54 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Tavis Ormandy , Kees Cook , Robert Swiecki Subject: [36/49] install_special_mapping skips security_file_mmap check. In-Reply-To: <20110105234415.GA22369@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let us know. ------------------ From: Tavis Ormandy commit 462e635e5b73ba9a4c03913b77138cd57ce4b050 upstream. The install_special_mapping routine (used, for example, to setup the vdso) skips the security check before insert_vm_struct, allowing a local attacker to bypass the mmap_min_addr security restriction by limiting the available pages for special mappings. bprm_mm_init() also skips the check, and although I don't think this can be used to bypass any restrictions, I don't see any reason not to have the security check. $ uname -m x86_64 $ cat /proc/sys/vm/mmap_min_addr 65536 $ cat install_special_mapping.s section .bss resb BSS_SIZE section .text global _start _start: mov eax, __NR_pause int 0x80 $ nasm -D__NR_pause=29 -DBSS_SIZE=0xfffed000 -f elf -o install_special_mapping.o install_special_mapping.s $ ld -m elf_i386 -Ttext=0x10000 -Tbss=0x11000 -o install_special_mapping install_special_mapping.o $ ./install_special_mapping & [1] 14303 $ cat /proc/14303/maps 0000f000-00010000 r-xp 00000000 00:00 0 [vdso] 00010000-00011000 r-xp 00001000 00:19 2453665 /home/taviso/install_special_mapping 00011000-ffffe000 rwxp 00000000 00:00 0 [stack] It's worth noting that Red Hat are shipping with mmap_min_addr set to 4096. Signed-off-by: Tavis Ormandy Acked-by: Kees Cook Acked-by: Robert Swiecki [ Changed to not drop the error code - akpm ] Reviewed-by: James Morris Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 5 +++++ mm/mmap.c | 16 ++++++++++++---- 2 files changed, 17 insertions(+), 4 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -247,6 +247,11 @@ static int __bprm_mm_init(struct linux_b vma->vm_start = vma->vm_end - PAGE_SIZE; vma->vm_flags = VM_STACK_FLAGS; vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); + + err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1); + if (err) + goto err; + err = insert_vm_struct(mm, vma); if (err) goto err; --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2290,6 +2290,7 @@ int install_special_mapping(struct mm_st unsigned long addr, unsigned long len, unsigned long vm_flags, struct page **pages) { + int ret; struct vm_area_struct *vma; vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); @@ -2306,16 +2307,23 @@ int install_special_mapping(struct mm_st vma->vm_ops = &special_mapping_vmops; vma->vm_private_data = pages; - if (unlikely(insert_vm_struct(mm, vma))) { - kmem_cache_free(vm_area_cachep, vma); - return -ENOMEM; - } + ret = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1); + if (ret) + goto out; + + ret = insert_vm_struct(mm, vma); + if (ret) + goto out; mm->total_vm += len >> PAGE_SHIFT; perf_event_mmap(vma); return 0; + +out: + kmem_cache_free(vm_area_cachep, vma); + return ret; } static DEFINE_MUTEX(mm_all_locks_mutex);