| Message ID | 20170615011203.144108-3-thgarnie@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jun 14, 2017 at 06:12:03PM -0700, Thomas Garnier wrote: > 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 <thgarnie@google.com> > --- > v10 redesigns the change to use work flags on set_fs as recommended by > Linus and agreed by others. > > Based on next-20170609 > --- > 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(-) For arm64: Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
On Wed, Jun 21, 2017 at 1:16 AM, Catalin Marinas <catalin.marinas@arm.com> wrote: > On Wed, Jun 14, 2017 at 06:12:03PM -0700, Thomas Garnier wrote: >> 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 <thgarnie@google.com> >> --- >> v10 redesigns the change to use work flags on set_fs as recommended by >> Linus and agreed by others. >> >> Based on next-20170609 >> --- >> 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(-) > > For arm64: > > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Thanks Catalin
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 <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();
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 <thgarnie@google.com> --- v10 redesigns the change to use work flags on set_fs as recommended by Linus and agreed by others. Based on next-20170609 --- 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(-)