svn commit: r192035 - in head/sys: amd64/amd64 i386/i386

[Alan Cox]

Author: alc
Date: Wed May 13 07:42:53 2009
New Revision: 192035
URL: http://svn.freebsd.org/changeset/base/192035

Log:
  Correct a rare use-after-free error in pmap_copy().  This error was
  introduced in amd64 revision 1.540 and i386 revision 1.547.  However, it
  had no harmful effects until after a recent change, r189698, on amd64.
  (In other words, the error is harmless in RELENG_7.)
  
  The error is triggered by the failure to allocate a pv entry for the one
  and only mapping in a page table page.  I am addressing the error by
  changing pmap_copy() to abort if either pv entry allocation or page
  table page allocation fails.  This is appropriate because the creation of
  mappings by pmap_copy() is optional.  They are a (possible) optimization,
  and not a requirement.
  
  Correct a nearby whitespace error in the i386 pmap_copy().
  
  Crash reported by: jeff@
  MFC after:	6 weeks

Modified:
  head/sys/amd64/amd64/pmap.c
  head/sys/i386/i386/pmap.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Wed May 13 05:39:39 2009	(r192034)
+++ head/sys/amd64/amd64/pmap.c	Wed May 13 07:42:53 2009	(r192035)
@@ -3556,7 +3556,7 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pm
 					dstmpte->wire_count++;
 				else if ((dstmpte = pmap_allocpte(dst_pmap,
 				    addr, M_NOWAIT)) == NULL)
-					break;
+					goto out;
 				dst_pte = (pt_entry_t *)
 				    PHYS_TO_DMAP(VM_PAGE_TO_PHYS(dstmpte));
 				dst_pte = &dst_pte[pmap_pte_index(addr)];
@@ -3579,6 +3579,7 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pm
 					 	    addr);
 				    	    	pmap_free_zero_pages(free);
 					}
+					goto out;
 				}
 				if (dstmpte->wire_count >= srcmpte->wire_count)
 					break;
@@ -3587,6 +3588,7 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pm
 			src_pte++;
 		}
 	}
+out:
 	vm_page_unlock_queues();
 	PMAP_UNLOCK(src_pmap);
 	PMAP_UNLOCK(dst_pmap);

Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c	Wed May 13 05:39:39 2009	(r192034)
+++ head/sys/i386/i386/pmap.c	Wed May 13 07:42:53 2009	(r192035)
@@ -3638,7 +3638,7 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pm
 				dstmpte = pmap_allocpte(dst_pmap, addr,
 				    M_NOWAIT);
 				if (dstmpte == NULL)
-					break;
+					goto out;
 				dst_pte = pmap_pte_quick(dst_pmap, addr);
 				if (*dst_pte == 0 &&
 				    pmap_try_insert_pv_entry(dst_pmap, addr,
@@ -3653,12 +3653,13 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pm
 					dst_pmap->pm_stats.resident_count++;
 	 			} else {
 					free = NULL;
-					if (pmap_unwire_pte_hold( dst_pmap,
+					if (pmap_unwire_pte_hold(dst_pmap,
 					    dstmpte, &free)) {
 						pmap_invalidate_page(dst_pmap,
 						    addr);
 						pmap_free_zero_pages(free);
 					}
+					goto out;
 				}
 				if (dstmpte->wire_count >= srcmpte->wire_count)
 					break;
@@ -3667,6 +3668,7 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pm
 			src_pte++;
 		}
 	}
+out:
 	sched_unpin();
 	vm_page_unlock_queues();
 	PMAP_UNLOCK(src_pmap);