From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752710AbdGHMQ5 (ORCPT ); Sat, 8 Jul 2017 08:16:57 -0400 Received: from terminus.zytor.com ([65.50.211.136]:60117 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750982AbdGHMQy (ORCPT ); Sat, 8 Jul 2017 08:16:54 -0400 Date: Sat, 8 Jul 2017 05:09:53 -0700 From: tip-bot for Thomas Garnier Message-ID: Cc: dave.hansen@intel.com, dhowells@redhat.com, linux@armlinux.org.uk, hpa@zytor.com, pmladek@suse.com, catalin.marinas@arm.com, tglx@linutronix.de, oleg@redhat.com, pbonzini@redhat.com, mingo@kernel.org, cmetcalf@mellanox.com, riel@redhat.com, will.deacon@arm.com, mbenes@suse.cz, jpoimboe@redhat.com, thgarnie@google.com, luto@amacapital.net, luto@kernel.org, wad@chromium.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, arnd@arndb.de, keescook@chromium.org, panand@redhat.com, viro@zeniv.linux.org.uk Reply-To: luto@kernel.org, luto@amacapital.net, thgarnie@google.com, jpoimboe@redhat.com, mbenes@suse.cz, wad@chromium.org, arnd@arndb.de, keescook@chromium.org, mark.rutland@arm.com, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, panand@redhat.com, hpa@zytor.com, dhowells@redhat.com, linux@armlinux.org.uk, dave.hansen@intel.com, pbonzini@redhat.com, oleg@redhat.com, catalin.marinas@arm.com, tglx@linutronix.de, pmladek@suse.com, will.deacon@arm.com, riel@redhat.com, cmetcalf@mellanox.com, mingo@kernel.org In-Reply-To: <20170615011203.144108-1-thgarnie@google.com> References: <20170615011203.144108-1-thgarnie@google.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/syscall] x86/syscalls: Check address limit on user-mode return Git-Commit-ID: 5ea0727b163cb5575e36397a12eade68a1f35f24 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 5ea0727b163cb5575e36397a12eade68a1f35f24 Gitweb: http://git.kernel.org/tip/5ea0727b163cb5575e36397a12eade68a1f35f24 Author: Thomas Garnier AuthorDate: Wed, 14 Jun 2017 18:12:01 -0700 Committer: Thomas Gleixner CommitDate: Sat, 8 Jul 2017 14:05:32 +0200 x86/syscalls: Check address limit on user-mode return Ensure the address limit is a user-mode segment before returning to user-mode. Otherwise a process can corrupt kernel-mode memory and elevate privileges [1]. The set_fs function sets the TIF_SETFS flag to force a slow path on return. In the slow path, the address limit is checked to be USER_DS if needed. The addr_limit_user_check function is added as a cross-architecture function to check the address limit. [1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990 Signed-off-by: Thomas Garnier Signed-off-by: Thomas Gleixner Cc: Mark Rutland Cc: kernel-hardening@lists.openwall.com Cc: Catalin Marinas Cc: Will Deacon Cc: David Howells Cc: Dave Hansen Cc: Miroslav Benes Cc: Chris Metcalf Cc: Pratyush Anand Cc: Russell King Cc: Petr Mladek Cc: Rik van Riel Cc: Kees Cook Cc: Arnd Bergmann Cc: Al Viro Cc: Andy Lutomirski Cc: Josh Poimboeuf Cc: linux-arm-kernel@lists.infradead.org Cc: Will Drewry Cc: linux-api@vger.kernel.org Cc: Oleg Nesterov Cc: Andy Lutomirski Cc: Paolo Bonzini Link: http://lkml.kernel.org/r/20170615011203.144108-1-thgarnie@google.com --- arch/x86/entry/common.c | 3 +++ arch/x86/include/asm/thread_info.h | 5 ++++- arch/x86/include/asm/uaccess.h | 7 ++++++- include/linux/syscalls.h | 16 ++++++++++++++++ 4 files changed, 29 insertions(+), 2 deletions(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index cdefcfd..03505ff 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include @@ -183,6 +184,8 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs) struct thread_info *ti = current_thread_info(); u32 cached_flags; + addr_limit_user_check(); + if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled())) local_irq_disable(); diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index e00e1bd..5161da1a 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -98,6 +98,7 @@ struct thread_info { #define TIF_SYSCALL_TRACEPOINT 28 /* syscall tracepoint instrumentation */ #define TIF_ADDR32 29 /* 32-bit address space on 64 bits */ #define TIF_X32 30 /* 32-bit native x86-64 binary */ +#define TIF_FSCHECK 31 /* Check FS is USER_DS on return */ #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) @@ -122,6 +123,7 @@ struct thread_info { #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT) #define _TIF_ADDR32 (1 << TIF_ADDR32) #define _TIF_X32 (1 << TIF_X32) +#define _TIF_FSCHECK (1 << TIF_FSCHECK) /* * work to do in syscall_trace_enter(). Also includes TIF_NOHZ for @@ -137,7 +139,8 @@ struct thread_info { (_TIF_SYSCALL_TRACE | _TIF_NOTIFY_RESUME | _TIF_SIGPENDING | \ _TIF_NEED_RESCHED | _TIF_SINGLESTEP | _TIF_SYSCALL_EMU | \ _TIF_SYSCALL_AUDIT | _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE | \ - _TIF_PATCH_PENDING | _TIF_NOHZ | _TIF_SYSCALL_TRACEPOINT) + _TIF_PATCH_PENDING | _TIF_NOHZ | _TIF_SYSCALL_TRACEPOINT | \ + _TIF_FSCHECK) /* flags to check in __switch_to() */ #define _TIF_WORK_CTXSW \ diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index a059aac..11433f9 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -26,7 +26,12 @@ #define get_ds() (KERNEL_DS) #define get_fs() (current->thread.addr_limit) -#define set_fs(x) (current->thread.addr_limit = (x)) +static inline void set_fs(mm_segment_t fs) +{ + current->thread.addr_limit = fs; + /* On user-mode return, check fs is correct */ + set_thread_flag(TIF_FSCHECK); +} #define segment_eq(a, b) ((a).seg == (b).seg) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 980c3c9..ac0cf6f 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -206,6 +206,22 @@ extern struct trace_event_functions exit_syscall_print_funcs; } \ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)) +#ifdef TIF_FSCHECK +/* + * Called before coming back to user-mode. Returning to user-mode with an + * address limit different than USER_DS can allow to overwrite kernel memory. + */ +static inline void addr_limit_user_check(void) +{ + + if (!test_thread_flag(TIF_FSCHECK)) + return; + + BUG_ON(!segment_eq(get_fs(), USER_DS)); + clear_thread_flag(TIF_FSCHECK); +} +#endif + asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special, qid_t id, void __user *addr); asmlinkage long sys_time(time_t __user *tloc);