[PATCH v2 28/30] arm64: Implement thread_struct whitelist for hardened usercopy

[PATCH v2 28/30] arm64: Implement thread_struct whitelist for hardened usercopy

[Kees Cook]

This whitelists the FPU register state portion of the thread_struct for
copying to userspace, instead of the default entire structure.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: zijun_hu <zijun_hu@htc.com>
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/Kconfig                 | 1 +
 arch/arm64/include/asm/processor.h | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index dfd908630631..b773299bc4e3 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -73,6 +73,7 @@ config ARM64
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
 	select HAVE_ARCH_SECCOMP_FILTER
+	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select HAVE_ARM_SMCCC
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 64c9e78f9882..799f112e5ff7 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -90,6 +90,14 @@ struct thread_struct {
 	struct debug_info	debug;		/* debugging */
 };
 
+/* Whitelist the fpsimd_state for copying to userspace. */
+static inline void arch_thread_struct_whitelist(unsigned long *offset,
+						unsigned long *size)
+{
+	*offset = offsetof(struct thread_struct, fpsimd_state);
+	*size = sizeof(struct fpsimd_state);
+}
+
 #ifdef CONFIG_COMPAT
 #define task_user_tls(t)						\
 ({									\
-- 
2.7.4

[PATCH v2 29/30] arm: Implement thread_struct whitelist for hardened usercopy

[Kees Cook]

ARM does not carry FPU state in the thread structure, so it can declare
no usercopy whitelist at all.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm/Kconfig                 | 1 +
 arch/arm/include/asm/processor.h | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a208bfe367b5..3781f08d00fa 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -48,6 +48,7 @@ config ARM
 	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
 	select HAVE_ARCH_MMAP_RND_BITS if MMU
 	select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT)
+	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARM_SMCCC if CPU_V7
 	select HAVE_CBPF_JIT
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index c3d5fc124a05..d6dc45c92ee5 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -45,6 +45,13 @@ struct thread_struct {
 	struct debug_info	debug;
 };
 
+/* Nothing needs to be usercopy-whitelisted from thread_struct. */
+static inline void arch_thread_struct_whitelist(unsigned long *offset,
+						unsigned long *size)
+{
+	*offset = *size = 0;
+}
+
 #define INIT_THREAD  {	}
 
 #ifdef CONFIG_MMU
-- 
2.7.4