From 5ea0727b163cb5575e36397a12eade68a1f35f24 Mon Sep 17 00:00:00 2001 From: Thomas Garnier Date: Wed, 14 Jun 2017 18:12:01 -0700 Subject: 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 ++++++- 3 files changed, 13 insertions(+), 2 deletions(-) (limited to 'arch') diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index cdefcfdd9e63..03505ffbe1b6 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 e00e1bd6e7b3..5161da1a0fa0 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 a059aac9e937..11433f9018e2 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) -- cgit From 73ac5d6a2b6ac3ae8d1e1818f3e9946f97489bc9 Mon Sep 17 00:00:00 2001 From: Thomas Garnier Date: Wed, 14 Jun 2017 18:12:02 -0700 Subject: arm/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 TIF_SETFS flag is added to _TIF_WORK_MASK shifting _TIF_SYSCALL_WORK for arm instruction immediate support. The global work mask is too big to used on a single instruction so adapt ret_fast_syscall. [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/20170615011203.144108-2-thgarnie@google.com --- arch/arm/include/asm/thread_info.h | 15 +++++++++------ arch/arm/include/asm/uaccess.h | 2 ++ arch/arm/kernel/entry-common.S | 9 +++++++-- arch/arm/kernel/signal.c | 5 +++++ 4 files changed, 23 insertions(+), 8 deletions(-) (limited to 'arch') diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index 776757d1604a..1d468b527b7b 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -139,10 +139,11 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, #define TIF_NEED_RESCHED 1 /* rescheduling necessary */ #define TIF_NOTIFY_RESUME 2 /* callback before returning to user */ #define TIF_UPROBE 3 /* breakpointed or singlestepping */ -#define TIF_SYSCALL_TRACE 4 /* syscall trace active */ -#define TIF_SYSCALL_AUDIT 5 /* syscall auditing active */ -#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */ -#define TIF_SECCOMP 7 /* seccomp syscall filtering active */ +#define TIF_FSCHECK 4 /* Check FS is USER_DS on return */ +#define TIF_SYSCALL_TRACE 5 /* syscall trace active */ +#define TIF_SYSCALL_AUDIT 6 /* syscall auditing active */ +#define TIF_SYSCALL_TRACEPOINT 7 /* syscall tracepoint instrumentation */ +#define TIF_SECCOMP 8 /* seccomp syscall filtering active */ #define TIF_NOHZ 12 /* in adaptive nohz mode */ #define TIF_USING_IWMMXT 17 @@ -153,6 +154,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_UPROBE (1 << TIF_UPROBE) +#define _TIF_FSCHECK (1 << TIF_FSCHECK) #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT) @@ -166,8 +168,9 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, /* * Change these and you break ASM code in entry-common.S */ -#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ - _TIF_NOTIFY_RESUME | _TIF_UPROBE) +#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ + _TIF_NOTIFY_RESUME | _TIF_UPROBE | \ + _TIF_FSCHECK) #endif /* __KERNEL__ */ #endif /* __ASM_ARM_THREAD_INFO_H */ diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index 2577405d082d..6cc882223e34 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -77,6 +77,8 @@ static inline void set_fs(mm_segment_t fs) { current_thread_info()->addr_limit = fs; modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER); + /* On user-mode return, check fs is correct */ + set_thread_flag(TIF_FSCHECK); } #define segment_eq(a, b) ((a) == (b)) diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index eb5cd77bf1d8..e33c32d56193 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -41,7 +41,9 @@ ret_fast_syscall: UNWIND(.cantunwind ) disable_irq_notrace @ disable interrupts ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing - tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK + tst r1, #_TIF_SYSCALL_WORK + bne fast_work_pending + tst r1, #_TIF_WORK_MASK bne fast_work_pending /* perform architecture specific actions before user return */ @@ -67,12 +69,15 @@ ret_fast_syscall: str r0, [sp, #S_R0 + S_OFF]! @ save returned r0 disable_irq_notrace @ disable interrupts ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing - tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK + tst r1, #_TIF_SYSCALL_WORK + bne fast_work_pending + tst r1, #_TIF_WORK_MASK beq no_work_pending UNWIND(.fnend ) ENDPROC(ret_fast_syscall) /* Slower path - fall through to work_pending */ +fast_work_pending: #endif tst r1, #_TIF_SYSCALL_WORK diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index 7b8f2141427b..3a48b54c6405 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -571,6 +572,10 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) * Update the trace code with the current status. */ trace_hardirqs_off(); + + /* Check valid user FS if needed */ + addr_limit_user_check(); + do { if (likely(thread_flags & _TIF_NEED_RESCHED)) { schedule(); -- cgit From cf7de27ab35172a9240f079477cae3146a182998 Mon Sep 17 00:00:00 2001 From: Thomas Garnier Date: Wed, 14 Jun 2017 18:12:03 -0700 Subject: arm64/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. [1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990 Signed-off-by: Thomas Garnier Reviewed-by: Catalin Marinas Signed-off-by: Thomas Gleixner Cc: Mark Rutland Cc: kernel-hardening@lists.openwall.com 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/20170615011203.144108-3-thgarnie@google.com --- arch/arm64/include/asm/thread_info.h | 4 +++- arch/arm64/include/asm/uaccess.h | 3 +++ arch/arm64/kernel/signal.c | 5 +++++ 3 files changed, 11 insertions(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 46c3b93cf865..c5ba565544ee 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -86,6 +86,7 @@ struct thread_info { #define TIF_NOTIFY_RESUME 2 /* callback before returning to user */ #define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */ #define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */ +#define TIF_FSCHECK 5 /* Check FS is USER_DS on return */ #define TIF_NOHZ 7 #define TIF_SYSCALL_TRACE 8 #define TIF_SYSCALL_AUDIT 9 @@ -107,11 +108,12 @@ struct thread_info { #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT) #define _TIF_SECCOMP (1 << TIF_SECCOMP) #define _TIF_UPROBE (1 << TIF_UPROBE) +#define _TIF_FSCHECK (1 << TIF_FSCHECK) #define _TIF_32BIT (1 << TIF_32BIT) #define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \ - _TIF_UPROBE) + _TIF_UPROBE | _TIF_FSCHECK) #define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \ diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 7b8a04789cef..ced7a7c2dd41 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -45,6 +45,9 @@ static inline void set_fs(mm_segment_t fs) { current_thread_info()->addr_limit = fs; + /* On user-mode return, check fs is correct */ + set_thread_flag(TIF_FSCHECK); + /* * Enable/disable UAO so that copy_to_user() etc can access * kernel memory with the unprivileged instructions. diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index c7b6de62f9d3..0f0279148bdc 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include @@ -408,6 +409,10 @@ asmlinkage void do_notify_resume(struct pt_regs *regs, * Update the trace code with the current status. */ trace_hardirqs_off(); + + /* Check valid user FS if needed */ + addr_limit_user_check(); + do { if (thread_flags & _TIF_NEED_RESCHED) { schedule(); -- cgit