1 files changed, 46 insertions, 33 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 0add963a849b..8961b44f350c 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -210,28 +210,26 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
 		return true;
 	}
 
-	if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) &&
-	    !search_exception_tables(regs->nip)) {
-		pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n",
-				    address,
-				    from_kuid(&init_user_ns, current_uid()));
-	}
-
 	// Kernel fault on kernel address is bad
 	if (address >= TASK_SIZE)
 		return true;
 
-	// Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
-	if (!search_exception_tables(regs->nip))
-		return true;
+	// Read/write fault blocked by KUAP is bad, it can never succeed.
+	if (bad_kuap_fault(regs, address, is_write)) {
+		pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n",
+				    is_write ? "write" : "read", address,
+				    from_kuid(&init_user_ns, current_uid()));
 
-	// Read/write fault in a valid region (the exception table search passed
-	// above), but blocked by KUAP is bad, it can never succeed.
-	if (bad_kuap_fault(regs, address, is_write))
-		return true;
+		// Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
+		if (!search_exception_tables(regs->nip))
+			return true;
+
+		// Read/write fault in a valid region (the exception table search passed
+		// above), but blocked by KUAP is bad, it can never succeed.
+		return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read");
+	}
 
-	// What's left? Kernel fault on user in well defined regions (extable
-	// matched), and allowed by KUAP in the faulting context.
+	// What's left? Kernel fault on user and allowed by KUAP in the faulting context.
 	return false;
 }
 
@@ -303,7 +301,6 @@ static inline void cmo_account_page_fault(void)
 static inline void cmo_account_page_fault(void) { }
 #endif /* CONFIG_PPC_SMLPAR */
 
-#ifdef CONFIG_PPC_BOOK3S
 static void sanity_check_fault(bool is_write, bool is_user,
 			       unsigned long error_code, unsigned long address)
 {
@@ -320,6 +317,9 @@ static void sanity_check_fault(bool is_write, bool is_user,
 		return;
 	}
 
+	if (!IS_ENABLED(CONFIG_PPC_BOOK3S))
+		return;
+
 	/*
 	 * For hash translation mode, we should never get a
 	 * PROTFAULT. Any update to pte to reduce access will result in us
@@ -354,10 +354,6 @@ static void sanity_check_fault(bool is_write, bool is_user,
 
 	WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
 }
-#else
-static void sanity_check_fault(bool is_write, bool is_user,
-			       unsigned long error_code, unsigned long address) { }
-#endif /* CONFIG_PPC_BOOK3S */
 
 /*
  * Define the correct "is_write" bit in error_code based
@@ -365,17 +361,19 @@ static void sanity_check_fault(bool is_write, bool is_user,
  */
 #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
 #define page_fault_is_write(__err)	((__err) & ESR_DST)
-#define page_fault_is_bad(__err)	(0)
 #else
 #define page_fault_is_write(__err)	((__err) & DSISR_ISSTORE)
-#if defined(CONFIG_PPC_8xx)
+#endif
+
+#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
+#define page_fault_is_bad(__err)	(0)
+#elif defined(CONFIG_PPC_8xx)
 #define page_fault_is_bad(__err)	((__err) & DSISR_NOEXEC_OR_G)
 #elif defined(CONFIG_PPC64)
 #define page_fault_is_bad(__err)	((__err) & DSISR_BAD_FAULT_64S)
 #else
 #define page_fault_is_bad(__err)	((__err) & DSISR_BAD_FAULT_32S)
 #endif
-#endif
 
 /*
  * For 600- and 800-family processors, the error_code parameter is DSISR
@@ -547,10 +545,20 @@ NOKPROBE_SYMBOL(__do_page_fault);
 int do_page_fault(struct pt_regs *regs, unsigned long address,
 		  unsigned long error_code)
 {
+	const struct exception_table_entry *entry;
 	enum ctx_state prev_state = exception_enter();
 	int rc = __do_page_fault(regs, address, error_code);
 	exception_exit(prev_state);
-	return rc;
+	if (likely(!rc))
+		return 0;
+
+	entry = search_exception_tables(regs->nip);
+	if (unlikely(!entry))
+		return rc;
+
+	instruction_pointer_set(regs, extable_fixup(entry));
+
+	return 0;
 }
 NOKPROBE_SYMBOL(do_page_fault);
 
@@ -559,17 +567,10 @@ NOKPROBE_SYMBOL(do_page_fault);
  * It is called from the DSI and ISI handlers in head.S and from some
  * of the procedures in traps.c.
  */
-void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+void __bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 {
-	const struct exception_table_entry *entry;
 	int is_write = page_fault_is_write(regs->dsisr);
 
-	/* Are we prepared to handle this fault?  */
-	if ((entry = search_exception_tables(regs->nip)) != NULL) {
-		regs->nip = extable_fixup(entry);
-		return;
-	}
-
 	/* kernel has accessed a bad area */
 
 	switch (TRAP(regs)) {
@@ -603,3 +604,15 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 
 	die("Kernel access of bad area", regs, sig);
 }
+
+void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+{
+	const struct exception_table_entry *entry;
+
+	/* Are we prepared to handle this fault?  */
+	entry = search_exception_tables(instruction_pointer(regs));
+	if (entry)
+		instruction_pointer_set(regs, extable_fixup(entry));
+	else
+		__bad_page_fault(regs, address, sig);
+}