From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Garnier Subject: [PATCH v2 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state Date: Wed, 8 Mar 2017 17:24:54 -0800 Message-ID: <20170309012456.5631-2-thgarnie@google.com> References: <20170309012456.5631-1-thgarnie@google.com> Return-path: List-Post: List-Help: List-Unsubscribe: List-Subscribe: In-Reply-To: <20170309012456.5631-1-thgarnie@google.com> To: David Howells , Dave Hansen , Arnd Bergmann , Al Viro , =?UTF-8?q?Ren=C3=A9=20Nyffenegger?= , Thomas Garnier , Andrew Morton , Kees Cook , "Paul E . McKenney" , "David S . Miller" , Andy Lutomirski , Ard Biesheuvel , Nicolas Pitre , Petr Mladek , Sebastian Andrzej Siewior , Sergey Senozhatsky , Helge Deller , Rik van Riel , Ingo Molnar , Oleg Nesterov , John Stultz , Thomas Gleixner , Pavel Cc: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, kernel-hardening@lists.openwall.com List-Id: linux-api@vger.kernel.org Implement specific usage of verify_pre_usermode_state for user-mode returns for x86. --- Based on next-20170308 --- arch/x86/Kconfig | 1 + arch/x86/entry/common.c | 3 +++ arch/x86/entry/entry_64.S | 19 +++++++++++++++++++ arch/x86/include/asm/pgtable_64_types.h | 11 +++++++++++ arch/x86/include/asm/processor.h | 11 ----------- 5 files changed, 34 insertions(+), 11 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 005df7c825f5..6d48e18e6f09 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -63,6 +63,7 @@ config X86 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO + select ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 370c42c7f046..525edbb77f03 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -180,6 +181,8 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs) struct thread_info *ti = current_thread_info(); u32 cached_flags; + verify_pre_usermode_state(); + if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled())) local_irq_disable(); diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index d2b2a2948ffe..b3527d31b91b 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -96,6 +96,19 @@ ENDPROC(native_usergs_sysret64) # define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ #endif +#ifdef CONFIG_BUG_ON_DATA_CORRUPTION +.macro VERIFY_PRE_USERMODE_STATE + call verify_pre_usermode_state +.endm +#else +/* Similar to set_fs(USER_DS) in verify_pre_usermode_state without a warning. */ +.macro VERIFY_PRE_USERMODE_STATE + movq PER_CPU_VAR(current_task), %rax + movq $TASK_SIZE_MAX, %rcx + movq %rcx, TASK_addr_limit(%rax) +.endm +#endif + /* * 64-bit SYSCALL instruction entry. Up to 6 arguments in registers. * @@ -201,6 +214,7 @@ entry_SYSCALL_64_fastpath: * It might end up jumping to the slow path. If it jumps, RAX * and all argument registers are clobbered. */ + call *sys_call_table(, %rax, 8) .Lentry_SYSCALL_64_after_fastpath_call: @@ -218,6 +232,11 @@ entry_SYSCALL_64_fastpath: testl $_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) jnz 1f + /* + * Check user-mode state on fast path return, the same check is done + * under the slow path through syscall_return_slowpath. + */ + VERIFY_PRE_USERMODE_STATE LOCKDEP_SYS_EXIT TRACE_IRQS_ON /* user mode is traced as IRQs on */ movq RIP(%rsp), %rcx diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 3a264200c62f..0fbbb79d058c 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -76,4 +76,15 @@ typedef struct { pteval_t pte; } pte_t; #define EARLY_DYNAMIC_PAGE_TABLES 64 +/* + * User space process size. 47bits minus one guard page. The guard + * page is necessary on Intel CPUs: if a SYSCALL instruction is at + * the highest possible canonical userspace address, then that + * syscall will enter the kernel with a non-canonical return + * address, and SYSRET will explode dangerously. We avoid this + * particular problem by preventing anything from being mapped + * at the maximum canonical address. + */ +#define TASK_SIZE_MAX ((_AC(1, UL) << 47) - PAGE_SIZE) + #endif /* _ASM_X86_PGTABLE_64_DEFS_H */ diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index f385eca5407a..9bc99d37133e 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -829,17 +829,6 @@ static inline void spin_lock_prefetch(const void *x) #define KSTK_ESP(task) (task_pt_regs(task)->sp) #else -/* - * User space process size. 47bits minus one guard page. The guard - * page is necessary on Intel CPUs: if a SYSCALL instruction is at - * the highest possible canonical userspace address, then that - * syscall will enter the kernel with a non-canonical return - * address, and SYSRET will explode dangerously. We avoid this - * particular problem by preventing anything from being mapped - * at the maximum canonical address. - */ -#define TASK_SIZE_MAX ((1UL << 47) - PAGE_SIZE) - /* This decides where the kernel will search for a free chunk of vm * space during mmap's. */ -- 2.12.0.246.ga2ecc84866-goog