Le 03/06/2021 à 10:41, Christophe Leroy a écrit :
PPC64 uses MMU features to enable/disable KUAP at boot time.
But feature fixups are applied way too early on PPC32.
Now that all KUAP related actions are in C following the
conversion of KUAP initial setup and context switch in C,
static branches can be used to enable/disable KUAP.
Signed-off-by: Christophe Leroy
---
arch/powerpc/include/asm/book3s/32/kup.h | 27 +++-
arch/powerpc/mm/book3s32/kuap.c | 11 ++
2 files changed, 33 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h
b/arch/powerpc/include/asm/book3s/32/kup.h
index 2854d970dabe..68fbe28c6d7e 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -9,11 +9,12 @@
#include
+extern struct static_key_false disable_kuap_key;
Same as 8xx, this needs to be exported for modules.
extern struct static_key_false disable_kuep_key;
static __always_inline bool kuap_is_disabled(void)
{
- return !IS_ENABLED(CONFIG_PPC_KUAP);
+ return !IS_ENABLED(CONFIG_PPC_KUAP) ||
static_branch_unlikely(_kuap_key);
}
static __always_inline bool kuep_is_disabled(void)
@@ -62,6 +63,9 @@ static inline void kuap_save_and_lock(struct pt_regs *regs)
u32 addr = kuap & 0xf000;
u32 end = kuap << 28;
+ if (kuap_is_disabled())
+ return;
+
regs->kuap = kuap;
if (unlikely(!kuap))
return;
@@ -79,6 +83,9 @@ static inline void kuap_kernel_restore(struct pt_regs *regs,
unsigned long kuap)
u32 addr = regs->kuap & 0xf000;
u32 end = regs->kuap << 28;
+ if (kuap_is_disabled())
+ return;
+
current->thread.kuap = regs->kuap;
if (unlikely(regs->kuap == kuap))
@@ -91,6 +98,9 @@ static inline unsigned long kuap_get_and_assert_locked(void)
{
unsigned long kuap = current->thread.kuap;
+ if (kuap_is_disabled())
+ return 0;
+
WARN_ON_ONCE(IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) && kuap != 0);
return kuap;
@@ -106,6 +116,9 @@ static __always_inline void allow_user_access(void __user
*to, const void __user
{
u32 addr, end;
+ if (kuap_is_disabled())
+ return;
+
BUILD_BUG_ON(!__builtin_constant_p(dir));
BUILD_BUG_ON(dir & ~KUAP_READ_WRITE);
@@ -128,6 +141,9 @@ static __always_inline void prevent_user_access(void __user *to, const void __us
{
u32 addr, end;
+ if (kuap_is_disabled())
+ return;
+
BUILD_BUG_ON(!__builtin_constant_p(dir));
if (dir & KUAP_CURRENT_WRITE) {
@@ -159,6 +175,9 @@ static inline unsigned long prevent_user_access_return(void)
unsigned long end = flags << 28;
void __user *to = (__force void __user *)addr;
+ if (kuap_is_disabled())
+ return 0;
+
if (flags)
prevent_user_access(to, to, end - addr, KUAP_READ_WRITE);
@@ -171,6 +190,9 @@ static inline void restore_user_access(unsigned long flags)
unsigned long end = flags << 28;
void __user *to = (__force void __user *)addr;
+ if (kuap_is_disabled())
+ return;
+
if (flags)
allow_user_access(to, to, end - addr, KUAP_READ_WRITE);
}
@@ -181,6 +203,9 @@ bad_kuap_fault(struct pt_regs *regs, unsigned long address,
bool is_write)
unsigned long begin = regs->kuap & 0xf000;
unsigned long end = regs->kuap << 28;
+ if (kuap_is_disabled())
+ return false;
+
return is_write && (address < begin || address >= end);
}
diff --git a/arch/powerpc/mm/book3s32/kuap.c b/arch/powerpc/mm/book3s32/kuap.c
index 5533ed92ab3d..a4ce6cdc28e5 100644
--- a/arch/powerpc/mm/book3s32/kuap.c
+++ b/arch/powerpc/mm/book3s32/kuap.c
@@ -3,15 +3,18 @@
#include
#include
+struct static_key_false disable_kuap_key;
+
void __init setup_kuap(bool disabled)
{
- kuap_update_sr(mfsr(0) | SR_KS, 0, TASK_SIZE);
+ if (!disabled)
+ kuap_update_sr(mfsr(0) | SR_KS, 0, TASK_SIZE);
if (smp_processor_id() != boot_cpuid)
return;
- pr_info("Activating Kernel Userspace Access Protection\n");
-
if (disabled)
- pr_warn("KUAP cannot be disabled yet on 6xx when compiled
in\n");
+ static_branch_enable(_kuap_key);
+ else
+ pr_info("Activating Kernel Userspace Access Protection\n");
}
