From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760988Ab3K0CJV (ORCPT ); Tue, 26 Nov 2013 21:09:21 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:38771 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754112Ab3K0A4f (ORCPT ); Tue, 26 Nov 2013 19:56:35 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vasily Kulikov , Kees Cook , "Luck, Tony" , Oleg Nesterov , "Eric W. Biederman" , Andrew Morton , Linus Torvalds Subject: [PATCH 3.4 22/39] exec/ptrace: fix get_dumpable() incorrect tests Date: Tue, 26 Nov 2013 16:56:46 -0800 Message-Id: <20131127005620.575724915@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.rc3 In-Reply-To: <20131127005619.011763867@linuxfoundation.org> References: <20131127005619.011763867@linuxfoundation.org> User-Agent: quilt/0.60-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook commit d049f74f2dbe71354d43d393ac3a188947811348 upstream. The get_dumpable() return value is not boolean. Most users of the function actually want to be testing for non-SUID_DUMP_USER(1) rather than SUID_DUMP_DISABLE(0). The SUID_DUMP_ROOT(2) is also considered a protected state. Almost all places did this correctly, excepting the two places fixed in this patch. Wrong logic: if (dumpable == SUID_DUMP_DISABLE) { /* be protective */ } or if (dumpable == 0) { /* be protective */ } or if (!dumpable) { /* be protective */ } Correct logic: if (dumpable != SUID_DUMP_USER) { /* be protective */ } or if (dumpable != 1) { /* be protective */ } Without this patch, if the system had set the sysctl fs/suid_dumpable=2, a user was able to ptrace attach to processes that had dropped privileges to that user. (This may have been partially mitigated if Yama was enabled.) The macros have been moved into the file that declares get/set_dumpable(), which means things like the ia64 code can see them too. CVE-2013-2929 Reported-by: Vasily Kulikov Signed-off-by: Kees Cook Cc: "Luck, Tony" Cc: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/ia64/include/asm/processor.h | 2 +- fs/exec.c | 6 ++++++ include/linux/binfmts.h | 3 --- include/linux/sched.h | 4 ++++ kernel/ptrace.c | 3 ++- 5 files changed, 13 insertions(+), 5 deletions(-) --- a/arch/ia64/include/asm/processor.h +++ b/arch/ia64/include/asm/processor.h @@ -322,7 +322,7 @@ struct thread_struct { regs->loadrs = 0; \ regs->r8 = get_dumpable(current->mm); /* set "don't zap registers" flag */ \ regs->r12 = new_sp - 16; /* allocate 16 byte scratch area */ \ - if (unlikely(!get_dumpable(current->mm))) { \ + if (unlikely(get_dumpable(current->mm) != SUID_DUMP_USER)) { \ /* \ * Zap scratch regs to avoid leaking bits between processes with different \ * uid/privileges. \ --- a/fs/exec.c +++ b/fs/exec.c @@ -2027,6 +2027,12 @@ static int __get_dumpable(unsigned long return (ret >= 2) ? 2 : ret; } +/* + * This returns the actual value of the suid_dumpable flag. For things + * that are using this for checking for privilege transitions, it must + * test against SUID_DUMP_USER rather than treating it as a boolean + * value. + */ int get_dumpable(struct mm_struct *mm) { return __get_dumpable(mm->flags); --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -113,9 +113,6 @@ extern void setup_new_exec(struct linux_ extern void would_dump(struct linux_binprm *, struct file *); extern int suid_dumpable; -#define SUID_DUMP_DISABLE 0 /* No setuid dumping */ -#define SUID_DUMP_USER 1 /* Dump as user of process */ -#define SUID_DUMP_ROOT 2 /* Dump as root */ /* Stack area protections */ #define EXSTACK_DEFAULT 0 /* Whatever the arch defaults to */ --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -404,6 +404,10 @@ static inline void arch_pick_mmap_layout extern void set_dumpable(struct mm_struct *mm, int value); extern int get_dumpable(struct mm_struct *mm); +#define SUID_DUMP_DISABLE 0 /* No setuid dumping */ +#define SUID_DUMP_USER 1 /* Dump as user of process */ +#define SUID_DUMP_ROOT 2 /* Dump as root */ + /* mm flags */ /* dumpable bits */ #define MMF_DUMPABLE 0 /* core dump is permitted */ --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -254,7 +254,8 @@ ok: smp_rmb(); if (task->mm) dumpable = get_dumpable(task->mm); - if (!dumpable && !ptrace_has_cap(task_user_ns(task), mode)) + if (dumpable != SUID_DUMP_USER && + !ptrace_has_cap(task_user_ns(task), mode)) return -EPERM; return security_ptrace_access_check(task, mode);