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Date:      Sun, 13 Oct 2019 06:56:45 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r353463 - head/sys/vm
Message-ID:  <201910130656.x9D6ujnS044334@repo.freebsd.org>
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Author: kib
Date: Sun Oct 13 06:56:45 2019
New Revision: 353463
URL: https://svnweb.freebsd.org/changeset/base/353463

Log:
  Restore nofaulting operations after r352807
  
  The TDP_NOFAULTING flag should be checked in vm_fault(), not in
  vm_fault_trap().  Otherwise kernel accesses to userspace, like
  vn_io_fault(), enter vm locking when it should not.
  
  Reported and tested by:	pho
  Reviewed by:	alc, markj
  Sponsored by:	The FreeBSD Foundation
  MFC after:	3 days
  Differential revision:	https://reviews.freebsd.org/D21992

Modified:
  head/sys/vm/vm_fault.c

Modified: head/sys/vm/vm_fault.c
==============================================================================
--- head/sys/vm/vm_fault.c	Sun Oct 13 05:11:53 2019	(r353462)
+++ head/sys/vm/vm_fault.c	Sun Oct 13 06:56:45 2019	(r353463)
@@ -554,15 +554,11 @@ int
 vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
     int fault_flags, int *signo, int *ucode)
 {
-	struct thread *td;
 	int result;
 
 	MPASS(signo == NULL || ucode != NULL);
-	td = curthread;
-	if ((td->td_pflags & TDP_NOFAULTING) != 0)
-		return (KERN_PROTECTION_FAILURE);
 #ifdef KTRACE
-	if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
+	if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT))
 		ktrfault(vaddr, fault_type);
 #endif
 	result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags,
@@ -574,7 +570,7 @@ vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot
 	    result == KERN_OUT_OF_BOUNDS,
 	    ("Unexpected Mach error %d from vm_fault()", result));
 #ifdef KTRACE
-	if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
+	if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND))
 		ktrfaultend(result);
 #endif
 	if (result != KERN_SUCCESS && signo != NULL) {
@@ -644,6 +640,10 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fa
 	bool dead, hardfault, is_first_object_locked;
 
 	VM_CNT_INC(v_vm_faults);
+
+	if ((curthread->td_pflags & TDP_NOFAULTING) != 0)
+		return (KERN_PROTECTION_FAILURE);
+
 	fs.vp = NULL;
 	faultcount = 0;
 	nera = -1;

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