From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754878AbZGUOnD (ORCPT ); Tue, 21 Jul 2009 10:43:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752398AbZGUOnB (ORCPT ); Tue, 21 Jul 2009 10:43:01 -0400 Received: from mx2.redhat.com ([66.187.237.31]:47440 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750893AbZGUOnA (ORCPT ); Tue, 21 Jul 2009 10:43:00 -0400 From: Eric Paris Subject: [PATCH 1/2] VM/SELinux: require CAP_SYS_RAWIO for all mmap_zero operations To: linux-kernel@vger.kernel.org, selinux@tycho.nsa.gov, linux-security-module@vger.kernel.org Cc: sds@tycho.nsa.gov, jmorris@namei.org, spender@grsecurity.net, dwalsh@redhat.com, cl@linux-foundation.org, arjan@infradead.org, alan@lxorguk.ukuu.org.uk, kyle@mcmartin.ca, cpardy@redhat.com, arnd@arndb.de Date: Tue, 21 Jul 2009 10:41:58 -0400 Message-ID: <20090721144157.14159.23439.stgit@paris.rdu.redhat.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently non-SELinux systems need CAP_SYS_RAWIO for an application to mmap the 0 page. On SELinux systems they need a specific SELinux permission, but do not need CAP_SYS_RAWIO. This has proved to be a poor decision by the SELinux team as, by default, SELinux users are logged in unconfined and thus a malicious non-root has nothing stopping them from mapping the 0 page of virtual memory. On a non-SELinux system, a malicious non-root user is unable to do this, as they need CAP_SYS_RAWIO. This patch checks CAP_SYS_RAWIO for all operations which attemt to map a page below mmap_min_addr. Signed-off-by: Eric Paris --- include/linux/security.h | 2 -- mm/mmap.c | 10 ++++++++++ mm/mremap.c | 8 ++++++++ mm/nommu.c | 3 +++ security/capability.c | 2 -- 5 files changed, 21 insertions(+), 4 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index 1459091..f7d198a 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -2197,8 +2197,6 @@ static inline int security_file_mmap(struct file *file, unsigned long reqprot, unsigned long addr, unsigned long addr_only) { - if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) - return -EACCES; return 0; } diff --git a/mm/mmap.c b/mm/mmap.c index 34579b2..37fdc90 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1047,6 +1047,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, } } + if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) + return -EACCES; + error = security_file_mmap(file, reqprot, prot, flags, addr, 0); if (error) return error; @@ -1657,6 +1660,10 @@ static int expand_downwards(struct vm_area_struct *vma, return -ENOMEM; address &= PAGE_MASK; + + if ((address < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) + return -EACCES; + error = security_file_mmap(NULL, 0, 0, 0, address, 1); if (error) return error; @@ -1998,6 +2005,9 @@ unsigned long do_brk(unsigned long addr, unsigned long len) if (is_hugepage_only_range(mm, addr, len)) return -EINVAL; + if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) + return -EACCES; + error = security_file_mmap(NULL, 0, 0, 0, addr, 1); if (error) return error; diff --git a/mm/mremap.c b/mm/mremap.c index a39b7b9..066e73d 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -299,6 +299,10 @@ unsigned long do_mremap(unsigned long addr, if ((addr <= new_addr) && (addr+old_len) > new_addr) goto out; + ret = -EACCES; + if ((new_addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) + goto out; + ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); if (ret) goto out; @@ -407,6 +411,10 @@ unsigned long do_mremap(unsigned long addr, goto out; } + ret = -EACCES; + if ((new_addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) + goto out; + ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); if (ret) goto out; diff --git a/mm/nommu.c b/mm/nommu.c index 53cab10..c1f3eff 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -995,6 +995,9 @@ static int validate_mmap_request(struct file *file, } /* allow the security API to have its say */ + if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) + return -EACCES; + ret = security_file_mmap(file, reqprot, prot, flags, addr, 0); if (ret < 0) return ret; diff --git a/security/capability.c b/security/capability.c index f218dd3..a3a5d9b 100644 --- a/security/capability.c +++ b/security/capability.c @@ -334,8 +334,6 @@ static int cap_file_mmap(struct file *file, unsigned long reqprot, unsigned long prot, unsigned long flags, unsigned long addr, unsigned long addr_only) { - if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) - return -EACCES; return 0; }