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 ++ 2 files changed, 11 insertions(+), 6 deletions(-) (limited to 'arch/arm/include/asm') 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)) -- cgit