Merge tag 'powerpc-5.11-8' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fix from Michael Ellerman:
 "One fix for a regression seen in io_uring, introduced by our support
  for KUAP (Kernel User Access Prevention) with the Hash MMU.

  Thanks to Aneesh Kumar K.V, and Zorro Lang"

* tag 'powerpc-5.11-8' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/kuap: Allow kernel thread to access userspace after kthread_use_mm

Author: torvalds

arch/powerpc/include/asm/book3s/64/kup.h

@@ -199,25 +199,31 @@ DECLARE_STATIC_KEY_FALSE(uaccess_flush_key);
 
 #ifdef CONFIG_PPC_PKEY
 
+extern u64 __ro_after_init default_uamor;
+extern u64 __ro_after_init default_amr;
+extern u64 __ro_after_init default_iamr;
+
 #include <asm/mmu.h>
 #include <asm/ptrace.h>
 
-/*
- * For kernel thread that doesn't have thread.regs return
- * default AMR/IAMR values.
+/* usage of kthread_use_mm() should inherit the
+ * AMR value of the operating address space. But, the AMR value is
+ * thread-specific and we inherit the address space and not thread
+ * access restrictions. Because of this ignore AMR value when accessing
+ * userspace via kernel thread.
  */
 static inline u64 current_thread_amr(void)
 {
 	if (current->thread.regs)
 		return current->thread.regs->amr;
-	return AMR_KUAP_BLOCKED;
+	return default_amr;
 }
 
 static inline u64 current_thread_iamr(void)
 {
 	if (current->thread.regs)
 		return current->thread.regs->iamr;
-	return AMR_KUEP_BLOCKED;
+	return default_iamr;
 }
 #endif /* CONFIG_PPC_PKEY */
 

arch/powerpc/include/asm/book3s/64/pkeys.h

@@ -5,10 +5,6 @@
 
 #include <asm/book3s/64/hash-pkey.h>
 
-extern u64 __ro_after_init default_uamor;
-extern u64 __ro_after_init default_amr;
-extern u64 __ro_after_init default_iamr;
-
 static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags)
 {
 	if (!mmu_has_feature(MMU_FTR_PKEY))

arch/powerpc/mm/book3s64/pkeys.c

@@ -31,6 +31,7 @@ static u32 initial_allocation_mask __ro_after_init;
 u64 default_amr __ro_after_init  = ~0x0UL;
 u64 default_iamr __ro_after_init = 0x5555555555555555UL;
 u64 default_uamor __ro_after_init;
+EXPORT_SYMBOL(default_amr);
 /*
  * Key used to implement PROT_EXEC mmap. Denies READ/WRITE
  * We pick key 2 because 0 is special key and 1 is reserved as per ISA.