From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:33868 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753426AbdHUA3E (ORCPT ); Sun, 20 Aug 2017 20:29:04 -0400 Subject: Patch "Sanitize 'move_pages()' permission checks" has been added to the 4.4-stable tree To: torvalds@linux-foundation.org, ebiederm@xmission.com, gregkh@linuxfoundation.org, otto.ebeling@iki.fi, w@1wt.eu Cc: , From: Date: Sun, 20 Aug 2017 17:29:07 -0700 Message-ID: <150327534785210@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled Sanitize 'move_pages()' permission checks to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sanitize-move_pages-permission-checks.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 197e7e521384a23b9e585178f3f11c9fa08274b9 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 20 Aug 2017 13:26:27 -0700 Subject: Sanitize 'move_pages()' permission checks From: Linus Torvalds commit 197e7e521384a23b9e585178f3f11c9fa08274b9 upstream. The 'move_paghes()' system call was introduced long long ago with the same permission checks as for sending a signal (except using CAP_SYS_NICE instead of CAP_SYS_KILL for the overriding capability). That turns out to not be a great choice - while the system call really only moves physical page allocations around (and you need other capabilities to do a lot of it), you can check the return value to map out some the virtual address choices and defeat ASLR of a binary that still shares your uid. So change the access checks to the more common 'ptrace_may_access()' model instead. This tightens the access checks for the uid, and also effectively changes the CAP_SYS_NICE check to CAP_SYS_PTRACE, but it's unlikely that anybody really _uses_ this legacy system call any more (we hav ebetter NUMA placement models these days), so I expect nobody to notice. Famous last words. Reported-by: Otto Ebeling Acked-by: Eric W. Biederman Cc: Willy Tarreau Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/migrate.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -38,6 +38,7 @@ #include #include #include +#include #include @@ -1483,7 +1484,6 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, const int __user *, nodes, int __user *, status, int, flags) { - const struct cred *cred = current_cred(), *tcred; struct task_struct *task; struct mm_struct *mm; int err; @@ -1507,14 +1507,9 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, /* * Check if this process has the right to modify the specified - * process. The right exists if the process has administrative - * capabilities, superuser privileges or the same - * userid as the target process. - */ - tcred = __task_cred(task); - if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) && - !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) && - !capable(CAP_SYS_NICE)) { + * process. Use the regular "ptrace_may_access()" checks. + */ + if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { rcu_read_unlock(); err = -EPERM; goto out; Patches currently in stable-queue which might be from torvalds@linux-foundation.org are queue-4.4/x86-asm-64-clear-ac-on-nmi-entries.patch queue-4.4/sanitize-move_pages-permission-checks.patch queue-4.4/mm-mempolicy-fix-use-after-free-when-calling-get_mempolicy.patch queue-4.4/mm-revert-x86_64-and-arm64-elf_et_dyn_base-base-changes.patch