Commit-ID: cf7de27ab35172a9240f079477cae3146a182998 Gitweb: http://git.kernel.org/tip/cf7de27ab35172a9240f079477cae3146a182998 Author: Thomas Garnier <[email protected]> AuthorDate: Wed, 14 Jun 2017 18:12:03 -0700 Committer: Thomas Gleixner <[email protected]> CommitDate: Sat, 8 Jul 2017 14:05:33 +0200
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 <[email protected]> Reviewed-by: Catalin Marinas <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: Mark Rutland <[email protected]> Cc: [email protected] Cc: Will Deacon <[email protected]> Cc: David Howells <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Miroslav Benes <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Pratyush Anand <[email protected]> Cc: Russell King <[email protected]> Cc: Petr Mladek <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Kees Cook <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Al Viro <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: [email protected] Cc: Will Drewry <[email protected]> Cc: [email protected] Cc: Oleg Nesterov <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Paolo Bonzini <[email protected]> Link: http://lkml.kernel.org/r/[email protected] --- 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(-) diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 46c3b93..c5ba565 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 7b8a047..ced7a7c 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 c7b6de6..0f02791 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -25,6 +25,7 @@ #include <linux/uaccess.h> #include <linux/tracehook.h> #include <linux/ratelimit.h> +#include <linux/syscalls.h> #include <asm/debug-monitors.h> #include <asm/elf.h> @@ -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();
