1 files changed, 91 insertions, 53 deletions

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 2418f1efabd8..2bc828a1940c 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -27,6 +27,13 @@
 
 #ifdef CONFIG_MMU
 
+bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
+{
+	unsigned long addr = (unsigned long)unsafe_src;
+
+	return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
+}
+
 /*
  * This is useful to dump out the page tables associated with
  * 'addr' in mm 'mm'.
@@ -85,6 +92,9 @@ void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
 			break;
 
 		pte = pte_offset_map(pmd, addr);
+		if (!pte)
+			break;
+
 		pr_cont(", *pte=%08llx", (long long)pte_val(*pte));
 #ifndef CONFIG_ARM_LPAE
 		pr_cont(", *ppte=%08llx",
@@ -125,8 +135,7 @@ static void die_kernel_fault(const char *msg, struct mm_struct *mm,
 	bust_spinlocks(1);
 	pr_alert("8<--- cut here ---\n");
 	pr_alert("Unable to handle kernel %s at virtual address %08lx when %s\n",
-		 msg, addr, fsr & FSR_LNX_PF ? "execute" :
-		 fsr & FSR_WRITE ? "write" : "read");
+		 msg, addr, fsr & FSR_LNX_PF ? "execute" : str_write_read(fsr & FSR_WRITE));
 
 	show_pte(KERN_ALERT, mm, addr);
 	die("Oops", regs, fsr);
@@ -216,9 +225,6 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 }
 
 #ifdef CONFIG_MMU
-#define VM_FAULT_BADMAP		((__force vm_fault_t)0x010000)
-#define VM_FAULT_BADACCESS	((__force vm_fault_t)0x020000)
-
 static inline bool is_permission_fault(unsigned int fsr)
 {
 	int fs = fsr_fs(fsr);
@@ -232,41 +238,36 @@ static inline bool is_permission_fault(unsigned int fsr)
 	return false;
 }
 
-static vm_fault_t __kprobes
-__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int flags,
-		unsigned long vma_flags, struct pt_regs *regs)
+#ifdef CONFIG_CPU_TTBR0_PAN
+static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
 {
-	struct vm_area_struct *vma = find_vma(mm, addr);
-	if (unlikely(!vma))
-		return VM_FAULT_BADMAP;
-
-	if (unlikely(vma->vm_start > addr)) {
-		if (!(vma->vm_flags & VM_GROWSDOWN))
-			return VM_FAULT_BADMAP;
-		if (addr < FIRST_USER_ADDRESS)
-			return VM_FAULT_BADMAP;
-		if (expand_stack(vma, addr))
-			return VM_FAULT_BADMAP;
-	}
+	struct svc_pt_regs *svcregs;
 
-	/*
-	 * ok, we have a good vm_area for this memory access, check the
-	 * permissions on the VMA allow for the fault which occurred.
-	 */
-	if (!(vma->vm_flags & vma_flags))
-		return VM_FAULT_BADACCESS;
+	/* If we are in user mode: permission granted */
+	if (user_mode(regs))
+		return true;
+
+	/* uaccess state saved above pt_regs on SVC exception entry */
+	svcregs = to_svc_pt_regs(regs);
 
-	return handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
+	return !(svcregs->ttbcr & TTBCR_EPD0);
+}
+#else
+static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
+{
+	return true;
 }
+#endif
 
 static int __kprobes
 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
 	int sig, code;
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
-	unsigned long vm_flags = VM_ACCESS_FLAGS;
+	vm_flags_t vm_flags = VM_ACCESS_FLAGS;
 
 	if (kprobe_page_fault(regs, fsr))
 		return 0;
@@ -302,30 +303,67 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 
 	/*
-	 * As per x86, we may deadlock here.  However, since the kernel only
-	 * validly references user space from well defined areas of the code,
-	 * we can bug out early if this is from code which shouldn't.
+	 * Privileged access aborts with CONFIG_CPU_TTBR0_PAN enabled are
+	 * routed via the translation fault mechanism. Check whether uaccess
+	 * is disabled while in kernel mode.
 	 */
-	if (!mmap_read_trylock(mm)) {
-		if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
+	if (!ttbr0_usermode_access_allowed(regs))
+		goto no_context;
+
+	if (!(flags & FAULT_FLAG_USER))
+		goto lock_mmap;
+
+	vma = lock_vma_under_rcu(mm, addr);
+	if (!vma)
+		goto lock_mmap;
+
+	if (!(vma->vm_flags & vm_flags)) {
+		vma_end_read(vma);
+		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+		fault = 0;
+		code = SEGV_ACCERR;
+		goto bad_area;
+	}
+	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
+	if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+		vma_end_read(vma);
+
+	if (!(fault & VM_FAULT_RETRY)) {
+		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+		goto done;
+	}
+	count_vm_vma_lock_event(VMA_LOCK_RETRY);
+	if (fault & VM_FAULT_MAJOR)
+		flags |= FAULT_FLAG_TRIED;
+
+	/* Quick path to respond to signals */
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
 			goto no_context;
+		return 0;
+	}
+lock_mmap:
+
 retry:
-		mmap_read_lock(mm);
-	} else {
-		/*
-		 * The above down_read_trylock() might have succeeded in
-		 * which case, we'll have missed the might_sleep() from
-		 * down_read()
-		 */
-		might_sleep();
-#ifdef CONFIG_DEBUG_VM
-		if (!user_mode(regs) &&
-		    !search_exception_tables(regs->ARM_pc))
-			goto no_context;
-#endif
+	vma = lock_mm_and_find_vma(mm, addr, regs);
+	if (unlikely(!vma)) {
+		fault = 0;
+		code = SEGV_MAPERR;
+		goto bad_area;
+	}
+
+	/*
+	 * ok, we have a good vm_area for this memory access, check the
+	 * permissions on the VMA allow for the fault which occurred.
+	 */
+	if (!(vma->vm_flags & vm_flags)) {
+		mmap_read_unlock(mm);
+		fault = 0;
+		code = SEGV_ACCERR;
+		goto bad_area;
 	}
 
-	fault = __do_page_fault(mm, addr, flags, vm_flags, regs);
+	fault = handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
 
 	/* If we need to retry but a fatal signal is pending, handle the
 	 * signal first. We do not need to release the mmap_lock because
@@ -349,13 +387,14 @@ retry:
 	}
 
 	mmap_read_unlock(mm);
+done:
 
-	/*
-	 * Handle the "normal" case first - VM_FAULT_MAJOR
-	 */
-	if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
+	/* Handle the "normal" case first */
+	if (likely(!(fault & VM_FAULT_ERROR)))
 		return 0;
 
+	code = SEGV_MAPERR;
+bad_area:
 	/*
 	 * If we are in kernel mode at this point, we
 	 * have no context to handle this fault with.
@@ -386,8 +425,6 @@ retry:
 		 * isn't in our memory map..
 		 */
 		sig = SIGSEGV;
-		code = fault == VM_FAULT_BADACCESS ?
-			SEGV_ACCERR : SEGV_MAPERR;
 	}
 
 	__do_user_fault(addr, fsr, sig, code, regs);
@@ -588,6 +625,7 @@ do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
 	if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
 		return;
 
+	pr_alert("8<--- cut here ---\n");
 	pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
 		inf->name, ifsr, addr);