1 files changed, 26 insertions, 13 deletions

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 0e5b4bc7b217..ed4330cc3f4e 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -198,9 +198,6 @@ __do_user_fault(unsigned long addr, unsigned int fsr, unsigned int sig,
 {
 	struct task_struct *tsk = current;
 
-	if (addr > TASK_SIZE)
-		harden_branch_predictor();
-
 #ifdef CONFIG_DEBUG_USER
 	if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
 	    ((user_debug & UDBG_BUS)  && (sig == SIGBUS))) {
@@ -269,8 +266,10 @@ do_kernel_address_page_fault(struct mm_struct *mm, unsigned long addr,
 		/*
 		 * Fault from user mode for a kernel space address. User mode
 		 * should not be faulting in kernel space, which includes the
-		 * vector/khelper page. Send a SIGSEGV.
+		 * vector/khelper page. Handle the branch predictor hardening
+		 * while interrupts are still disabled, then send a SIGSEGV.
 		 */
+		harden_branch_predictor();
 		__do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 	} else {
 		/*
@@ -485,16 +484,20 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
  * We enter here because the first level page table doesn't contain
  * a valid entry for the address.
  *
- * If the address is in kernel space (>= TASK_SIZE), then we are
- * probably faulting in the vmalloc() area.
+ * If this is a user address (addr < TASK_SIZE), we handle this as a
+ * normal page fault. This leaves the remainder of the function to handle
+ * kernel address translation faults.
  *
- * If the init_task's first level page tables contains the relevant
- * entry, we copy the it to this task.  If not, we send the process
- * a signal, fixup the exception, or oops the kernel.
+ * Since user mode is not permitted to access kernel addresses, pass these
+ * directly to do_kernel_address_page_fault() to handle.
  *
- * NOTE! We MUST NOT take any locks for this case. We may be in an
- * interrupt or a critical region, and should only copy the information
- * from the master page table, nothing more.
+ * Otherwise, we're probably faulting in the vmalloc() area, so try to fix
+ * that up. Note that we must not take any locks or enable interrupts in
+ * this case.
+ *
+ * If vmalloc() fixup fails, that means the non-leaf page tables did not
+ * contain an entry for this address, so handle this via
+ * do_kernel_address_page_fault().
  */
 #ifdef CONFIG_MMU
 static int __kprobes
@@ -560,7 +563,8 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
 	return 0;
 
 bad_area:
-	do_bad_area(addr, fsr, regs);
+	do_kernel_address_page_fault(current->mm, addr, fsr, regs);
+
 	return 0;
 }
 #else					/* CONFIG_MMU */
@@ -580,7 +584,16 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
 static int
 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
+	/*
+	 * If this is a kernel address, but from user mode, then userspace
+	 * is trying bad stuff. Invoke the branch predictor handling.
+	 * Interrupts are disabled here.
+	 */
+	if (addr >= TASK_SIZE && user_mode(regs))
+		harden_branch_predictor();
+
 	do_bad_area(addr, fsr, regs);
+
 	return 0;
 }
 #endif /* CONFIG_ARM_LPAE */