1 files changed, 194 insertions, 153 deletions

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 58f69fa07df9..2bc828a1940c 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -1,12 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/arch/arm/mm/fault.c
  *
  *  Copyright (C) 1995  Linus Torvalds
  *  Modifications for ARM processor (c) 1995-2004 Russell King
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 #include <linux/extable.h>
 #include <linux/signal.h>
@@ -20,8 +17,8 @@
 #include <linux/sched/debug.h>
 #include <linux/highmem.h>
 #include <linux/perf_event.h>
+#include <linux/kfence.h>
 
-#include <asm/pgtable.h>
 #include <asm/system_misc.h>
 #include <asm/system_info.h>
 #include <asm/tlbflush.h>
@@ -30,58 +27,43 @@
 
 #ifdef CONFIG_MMU
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
+bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
 {
-	int ret = 0;
-
-	if (!user_mode(regs)) {
-		/* kprobe_running() needs smp_processor_id() */
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, fsr))
-			ret = 1;
-		preempt_enable();
-	}
+	unsigned long addr = (unsigned long)unsafe_src;
 
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
-{
-	return 0;
+	return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
 }
-#endif
 
 /*
  * This is useful to dump out the page tables associated with
  * 'addr' in mm 'mm'.
  */
-void show_pte(struct mm_struct *mm, unsigned long addr)
+void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pgd;
 
 	if (!mm)
 		mm = &init_mm;
 
-	pr_alert("pgd = %p\n", mm->pgd);
 	pgd = pgd_offset(mm, addr);
-	pr_alert("[%08lx] *pgd=%08llx",
-			addr, (long long)pgd_val(*pgd));
+	printk("%s[%08lx] *pgd=%08llx", lvl, addr, (long long)pgd_val(*pgd));
 
 	do {
+		p4d_t *p4d;
 		pud_t *pud;
 		pmd_t *pmd;
 		pte_t *pte;
 
-		if (pgd_none(*pgd))
+		p4d = p4d_offset(pgd, addr);
+		if (p4d_none(*p4d))
 			break;
 
-		if (pgd_bad(*pgd)) {
+		if (p4d_bad(*p4d)) {
 			pr_cont("(bad)");
 			break;
 		}
 
-		pud = pud_offset(pgd, addr);
+		pud = pud_offset(p4d, addr);
 		if (PTRS_PER_PUD != 1)
 			pr_cont(", *pud=%08llx", (long long)pud_val(*pud));
 
@@ -110,6 +92,9 @@ void show_pte(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",
@@ -121,10 +106,43 @@ void show_pte(struct mm_struct *mm, unsigned long addr)
 	pr_cont("\n");
 }
 #else					/* CONFIG_MMU */
-void show_pte(struct mm_struct *mm, unsigned long addr)
+void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
 { }
 #endif					/* CONFIG_MMU */
 
+static inline bool is_write_fault(unsigned int fsr)
+{
+	return (fsr & FSR_WRITE) && !(fsr & FSR_CM);
+}
+
+static inline bool is_translation_fault(unsigned int fsr)
+{
+	int fs = fsr_fs(fsr);
+#ifdef CONFIG_ARM_LPAE
+	if ((fs & FS_MMU_NOLL_MASK) == FS_TRANS_NOLL)
+		return true;
+#else
+	if (fs == FS_L1_TRANS || fs == FS_L2_TRANS)
+		return true;
+#endif
+	return false;
+}
+
+static void die_kernel_fault(const char *msg, struct mm_struct *mm,
+			     unsigned long addr, unsigned int fsr,
+			     struct pt_regs *regs)
+{
+	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" : str_write_read(fsr & FSR_WRITE));
+
+	show_pte(KERN_ALERT, mm, addr);
+	die("Oops", regs, fsr);
+	bust_spinlocks(0);
+	make_task_dead(SIGKILL);
+}
+
 /*
  * Oops.  The kernel tried to access some page that wasn't present.
  */
@@ -132,6 +150,7 @@ static void
 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 		  struct pt_regs *regs)
 {
+	const char *msg;
 	/*
 	 * Are we prepared to handle this kernel fault?
 	 */
@@ -141,15 +160,17 @@ __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 	/*
 	 * No handler, we'll have to terminate things with extreme prejudice.
 	 */
-	bust_spinlocks(1);
-	pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
-		 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
-		 "paging request", addr);
+	if (addr < PAGE_SIZE) {
+		msg = "NULL pointer dereference";
+	} else {
+		if (is_translation_fault(fsr) &&
+		    kfence_handle_page_fault(addr, is_write_fault(fsr), regs))
+			return;
 
-	show_pte(mm, addr);
-	die("Oops", regs, fsr);
-	bust_spinlocks(0);
-	do_exit(SIGKILL);
+		msg = "paging request";
+	}
+
+	die_kernel_fault(msg, mm, addr, fsr, regs);
 }
 
 /*
@@ -157,19 +178,21 @@ __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
  * User mode accesses just cause a SIGSEGV
  */
 static void
-__do_user_fault(struct task_struct *tsk, unsigned long addr,
-		unsigned int fsr, unsigned int sig, int code,
-		struct pt_regs *regs)
+__do_user_fault(unsigned long addr, unsigned int fsr, unsigned int sig,
+		int code, struct pt_regs *regs)
 {
+	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))) {
-		printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
+		pr_err("8<--- cut here ---\n");
+		pr_err("%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
 		       tsk->comm, sig, addr, fsr);
-		show_pte(tsk->mm, addr);
+		show_pte(KERN_ERR, tsk->mm, addr);
 		show_regs(regs);
 	}
 #endif
@@ -183,7 +206,7 @@ __do_user_fault(struct task_struct *tsk, unsigned long addr,
 	tsk->thread.address = addr;
 	tsk->thread.error_code = fsr;
 	tsk->thread.trap_no = 14;
-	force_sig_fault(sig, code, (void __user *)addr, tsk);
+	force_sig_fault(sig, code, (void __user *)addr);
 }
 
 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
@@ -196,81 +219,59 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	 * have no context to handle this fault with.
 	 */
 	if (user_mode(regs))
-		__do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
+		__do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 	else
 		__do_kernel_fault(mm, addr, fsr, regs);
 }
 
 #ifdef CONFIG_MMU
-#define VM_FAULT_BADMAP		0x010000
-#define VM_FAULT_BADACCESS	0x020000
-
-/*
- * Check that the permissions on the VMA allow for the fault which occurred.
- * If we encountered a write fault, we must have write permission, otherwise
- * we allow any permission.
- */
-static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
+static inline bool is_permission_fault(unsigned int fsr)
 {
-	unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
-
-	if (fsr & FSR_WRITE)
-		mask = VM_WRITE;
-	if (fsr & FSR_LNX_PF)
-		mask = VM_EXEC;
-
-	return vma->vm_flags & mask ? false : true;
+	int fs = fsr_fs(fsr);
+#ifdef CONFIG_ARM_LPAE
+	if ((fs & FS_MMU_NOLL_MASK) == FS_PERM_NOLL)
+		return true;
+#else
+	if (fs == FS_L1_PERM || fs == FS_L2_PERM)
+		return true;
+#endif
+	return false;
 }
 
-static vm_fault_t __kprobes
-__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
-		unsigned int flags, struct task_struct *tsk)
+#ifdef CONFIG_CPU_TTBR0_PAN
+static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
 {
-	struct vm_area_struct *vma;
-	vm_fault_t fault;
-
-	vma = find_vma(mm, addr);
-	fault = VM_FAULT_BADMAP;
-	if (unlikely(!vma))
-		goto out;
-	if (unlikely(vma->vm_start > addr))
-		goto check_stack;
+	struct svc_pt_regs *svcregs;
 
-	/*
-	 * Ok, we have a good vm_area for this
-	 * memory access, so we can handle it.
-	 */
-good_area:
-	if (access_error(fsr, vma)) {
-		fault = VM_FAULT_BADACCESS;
-		goto out;
-	}
+	/* If we are in user mode: permission granted */
+	if (user_mode(regs))
+		return true;
 
-	return handle_mm_fault(vma, addr & PAGE_MASK, flags);
+	/* uaccess state saved above pt_regs on SVC exception entry */
+	svcregs = to_svc_pt_regs(regs);
 
-check_stack:
-	/* Don't allow expansion below FIRST_USER_ADDRESS */
-	if (vma->vm_flags & VM_GROWSDOWN &&
-	    addr >= FIRST_USER_ADDRESS && !expand_stack(vma, addr))
-		goto good_area;
-out:
-	return fault;
+	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 task_struct *tsk;
-	struct mm_struct *mm;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
 	int sig, code;
 	vm_fault_t fault;
-	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+	unsigned int flags = FAULT_FLAG_DEFAULT;
+	vm_flags_t vm_flags = VM_ACCESS_FLAGS;
 
-	if (notify_page_fault(regs, fsr))
+	if (kprobe_page_fault(regs, fsr))
 		return 0;
 
-	tsk = current;
-	mm  = tsk->mm;
 
 	/* Enable interrupts if they were enabled in the parent context. */
 	if (interrupts_enabled(regs))
@@ -285,79 +286,115 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 
 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
-	if (fsr & FSR_WRITE)
+
+	if (is_write_fault(fsr)) {
 		flags |= FAULT_FLAG_WRITE;
+		vm_flags = VM_WRITE;
+	}
+
+	if (fsr & FSR_LNX_PF) {
+		vm_flags = VM_EXEC;
+
+		if (is_permission_fault(fsr) && !user_mode(regs))
+			die_kernel_fault("execution of memory",
+					 mm, addr, fsr, 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 (!down_read_trylock(&mm->mmap_sem)) {
-		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:
-		down_read(&mm->mmap_sem);
-	} 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;
 	}
 
-	fault = __do_page_fault(mm, addr, fsr, flags, tsk);
+	/*
+	 * 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 = 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_sem because
+	 * signal first. We do not need to release the mmap_lock because
 	 * it would already be released in __lock_page_or_retry in
 	 * mm/filemap.c. */
-	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
+	if (fault_signal_pending(fault, regs)) {
 		if (!user_mode(regs))
 			goto no_context;
 		return 0;
 	}
 
-	/*
-	 * Major/minor page fault accounting is only done on the
-	 * initial attempt. If we go through a retry, it is extremely
-	 * likely that the page will be found in page cache at that point.
-	 */
+	/* The fault is fully completed (including releasing mmap lock) */
+	if (fault & VM_FAULT_COMPLETED)
+		return 0;
 
-	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
-	if (!(fault & VM_FAULT_ERROR) && flags & FAULT_FLAG_ALLOW_RETRY) {
-		if (fault & VM_FAULT_MAJOR) {
-			tsk->maj_flt++;
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-					regs, addr);
-		} else {
-			tsk->min_flt++;
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-					regs, addr);
-		}
+	if (!(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_RETRY) {
-			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
-			* of starvation. */
-			flags &= ~FAULT_FLAG_ALLOW_RETRY;
 			flags |= FAULT_FLAG_TRIED;
 			goto retry;
 		}
 	}
 
-	up_read(&mm->mmap_sem);
+	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.
@@ -388,11 +425,9 @@ retry:
 		 * isn't in our memory map..
 		 */
 		sig = SIGSEGV;
-		code = fault == VM_FAULT_BADACCESS ?
-			SEGV_ACCERR : SEGV_MAPERR;
 	}
 
-	__do_user_fault(tsk, addr, fsr, sig, code, regs);
+	__do_user_fault(addr, fsr, sig, code, regs);
 	return 0;
 
 no_context:
@@ -431,6 +466,7 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
 {
 	unsigned int index;
 	pgd_t *pgd, *pgd_k;
+	p4d_t *p4d, *p4d_k;
 	pud_t *pud, *pud_k;
 	pmd_t *pmd, *pmd_k;
 
@@ -445,13 +481,16 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
 	pgd = cpu_get_pgd() + index;
 	pgd_k = init_mm.pgd + index;
 
-	if (pgd_none(*pgd_k))
+	p4d = p4d_offset(pgd, addr);
+	p4d_k = p4d_offset(pgd_k, addr);
+
+	if (p4d_none(*p4d_k))
 		goto bad_area;
-	if (!pgd_present(*pgd))
-		set_pgd(pgd, *pgd_k);
+	if (!p4d_present(*p4d))
+		set_p4d(p4d, *p4d_k);
 
-	pud = pud_offset(pgd, addr);
-	pud_k = pud_offset(pgd_k, addr);
+	pud = pud_offset(p4d, addr);
+	pud_k = pud_offset(p4d_k, addr);
 
 	if (pud_none(*pud_k))
 		goto bad_area;
@@ -556,9 +595,10 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
 		return;
 
+	pr_alert("8<--- cut here ---\n");
 	pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 		inf->name, fsr, addr);
-	show_pte(current->mm, addr);
+	show_pte(KERN_ALERT, current->mm, addr);
 
 	arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
 		       fsr, 0);
@@ -585,6 +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);