Move page tables lock into the address space.

This is necessary to prevent races with invalidation. It is currently
possible that page tables are garbage collected while paging caches
refer to them. We must ensure that pages are held until caches can be
invalidated. This is not achieved by this goal alone, but moving locking
to outside the page tables themselves is a requisite.

PiperOrigin-RevId: 198920784
Change-Id: I66fffecd49cb14aa2e676a84a68cabfc0c8b3e9a

1 files changed, 0 insertions, 8 deletions

diff --git a/pkg/sentry/platform/ring0/pagetables/pagetables.go b/pkg/sentry/platform/ring0/pagetables/pagetables.go
index 2df6792f7..2a83bbff2 100644
--- a/pkg/sentry/platform/ring0/pagetables/pagetables.go
+++ b/pkg/sentry/platform/ring0/pagetables/pagetables.go
@@ -16,8 +16,6 @@
 package pagetables
 
 import (
-	"sync"
-
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
@@ -39,8 +37,6 @@ type Node struct {
 
 // PageTables is a set of page tables.
 type PageTables struct {
-	mu sync.Mutex
-
 	// root is the pagetable root.
 	root *Node
 
@@ -122,7 +118,6 @@ func (p *PageTables) Map(addr usermem.Addr, length uintptr, opts MapOpts, physic
 		return p.Unmap(addr, length)
 	}
 	prev := false
-	p.mu.Lock()
 	end, ok := addr.AddLength(uint64(length))
 	if !ok {
 		panic("pagetables.Map: overflow")
@@ -139,7 +134,6 @@ func (p *PageTables) Map(addr usermem.Addr, length uintptr, opts MapOpts, physic
 		}
 		pte.Set(p, opts)
 	})
-	p.mu.Unlock()
 	return prev
 }
 
@@ -147,13 +141,11 @@ func (p *PageTables) Map(addr usermem.Addr, length uintptr, opts MapOpts, physic
 //
 // True is returned iff there was a previous mapping in the range.
 func (p *PageTables) Unmap(addr usermem.Addr, length uintptr) bool {
-	p.mu.Lock()
 	count := 0
 	p.iterateRange(uintptr(addr), uintptr(addr)+length, false, func(s, e uintptr, pte *PTE, align uintptr) {
 		pte.Clear()
 		count++
 	})
-	p.mu.Unlock()
 	return count > 0
 }