Subject: [PATCH v2 15/28] powerpc/book3s64/pkeys: Reset userspace AMR correctly on exec

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Sat, 2 May 2020 16:52:16 +0530

On fork, we inherit from the parent and on exec, we should switch to default_amr values.

Also, avoid changing the AMR register value within the kernel. The kernel now runs with
different AMR values.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 arch/powerpc/include/asm/book3s/64/kup.h |  2 ++
 arch/powerpc/kernel/process.c            | 19 ++++++++++++++++++-
 arch/powerpc/mm/book3s64/pkeys.c         | 18 ++----------------
 3 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h
index 67320a990f3f..fe1818954e51 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h
@@ -171,6 +171,8 @@
 #include <asm/ptrace.h>
 
 extern u64 default_uamor;
+extern u64 default_amr;
+extern u64 default_iamr;
 
 static inline void kuap_restore_user_amr(struct pt_regs *regs)
 {
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9ef95a1217ef..0ab9a8cf1bcb 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1474,7 +1474,25 @@ void arch_setup_new_exec(void)
 		current->thread.regs = regs - 1;
 	}
 
+#ifdef CONFIG_PPC_MEM_KEYS
+	current->thread.regs->kuap  = default_amr;
+	current->thread.regs->kuep  = default_iamr;
+#endif
+
 }
+#else
+void arch_setup_new_exec(void)
+{
+	/*
+	 * If we exec out of a kernel thread then thread.regs will not be
+	 * set.  Do it now.
+	 */
+	if (!current->thread.regs) {
+		struct pt_regs *regs = task_stack_page(current) + THREAD_SIZE;
+		current->thread.regs = regs - 1;
+	}
+}
+
 #endif
 
 #ifdef CONFIG_PPC64
@@ -1809,7 +1827,6 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
 	current->thread.load_tm = 0;
 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
 
-	thread_pkey_regs_init(&current->thread);
 }
 EXPORT_SYMBOL(start_thread);
 
diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 976f65f27324..5012b57af808 100644
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -20,8 +20,8 @@ int  max_pkey;			/* Maximum key value supported */
  */
 u32  reserved_allocation_mask;
 static u32  initial_allocation_mask;   /* Bits set for the initially allocated keys */
-static u64 default_amr;
-static u64 default_iamr;
+u64 default_amr;
+u64 default_iamr;
 /* Allow all keys to be modified by default */
 u64 default_uamor = ~0x0UL;
 /*
@@ -387,20 +387,6 @@ void thread_pkey_regs_restore(struct thread_struct *new_thread,
 		write_uamor(new_thread->uamor);
 }
 
-void thread_pkey_regs_init(struct thread_struct *thread)
-{
-	if (!mmu_has_feature(MMU_FTR_PKEY))
-		return;
-
-	thread->amr   = default_amr;
-	thread->iamr  = default_iamr;
-	thread->uamor = default_uamor;
-
-	write_amr(default_amr);
-	write_iamr(default_iamr);
-	write_uamor(default_uamor);
-}
-
 int execute_only_pkey(struct mm_struct *mm)
 {
 	if (static_branch_likely(&execute_pkey_disabled))
-- 
2.26.2