Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754085Ab1BBAym (ORCPT ); Tue, 1 Feb 2011 19:54:42 -0500 Received: from mga02.intel.com ([134.134.136.20]:59105 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753671Ab1BBAou (ORCPT ); Tue, 1 Feb 2011 19:44:50 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.60,412,1291622400"; d="scan'208";a="703028556" From: Andi Kleen References: <20110201443.618138584@firstfloor.org> In-Reply-To: <20110201443.618138584@firstfloor.org> To: taviso@cmpxchg8b.com, taviso@google.com, kees@ubuntu.com, swiecki@google.com, ak@linux.intel.com, jmorris@namei.org, torvalds@linux-foundation.org, gregkh@suse.de, linux-kernel@vger.kernel.org, stable@kernel.org Subject: [PATCH] [97/139] install_special_mapping skips security_file_mmap check. Message-Id: <20110202004455.474BD3E09BD@tassilo.jf.intel.com> Date: Tue, 1 Feb 2011 16:44:55 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3784 Lines: 115 2.6.35-longterm review patch. If anyone has any objections, please let me 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 Signed-off-by: Andi Kleen [ 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(-) Index: linux-2.6.35.y/fs/exec.c =================================================================== --- linux-2.6.35.y.orig/fs/exec.c +++ linux-2.6.35.y/fs/exec.c @@ -265,6 +265,11 @@ static int __bprm_mm_init(struct linux_b vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); INIT_LIST_HEAD(&vma->anon_vma_chain); + + 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; Index: linux-2.6.35.y/mm/mmap.c =================================================================== --- linux-2.6.35.y.orig/mm/mmap.c +++ linux-2.6.35.y/mm/mmap.c @@ -2444,6 +2444,7 @@ 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); @@ -2461,16 +2462,23 @@ 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); -- 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/