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authorkib <kib@FreeBSD.org>2012-02-11 17:29:07 +0000
committerkib <kib@FreeBSD.org>2012-02-11 17:29:07 +0000
commitdacbfe950a81e3904fb15609934754d23432a328 (patch)
treee6a1bc83c2fa78afa49c7d25721b2e04105fc483 /sys/vm
parent3e86e21237c556aca42212d457e89b7ca8c54064 (diff)
downloadFreeBSD-src-dacbfe950a81e3904fb15609934754d23432a328.zip
FreeBSD-src-dacbfe950a81e3904fb15609934754d23432a328.tar.gz
Close a race due to dropping of the map lock between creating map entry
for a shared mapping and marking the entry for inheritance. Other thread might execute vmspace_fork() in between (e.g. by fork(2)), resulting in the mapping becoming private. Noted and reviewed by: alc MFC after: 1 week
Diffstat (limited to 'sys/vm')
-rw-r--r--sys/vm/vm_map.c9
-rw-r--r--sys/vm/vm_map.h2
-rw-r--r--sys/vm/vm_mmap.c10
3 files changed, 11 insertions, 10 deletions
diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index d62576f..0c98d56 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -1130,6 +1130,7 @@ vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
vm_map_entry_t temp_entry;
vm_eflags_t protoeflags;
struct ucred *cred;
+ vm_inherit_t inheritance;
boolean_t charge_prev_obj;
VM_MAP_ASSERT_LOCKED(map);
@@ -1173,6 +1174,10 @@ vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
protoeflags |= MAP_ENTRY_NOSYNC;
if (cow & MAP_DISABLE_COREDUMP)
protoeflags |= MAP_ENTRY_NOCOREDUMP;
+ if (cow & MAP_INHERIT_SHARE)
+ inheritance = VM_INHERIT_SHARE;
+ else
+ inheritance = VM_INHERIT_DEFAULT;
cred = NULL;
KASSERT((object != kmem_object && object != kernel_object) ||
@@ -1227,7 +1232,7 @@ charged:
* can extend the previous map entry to include the
* new range as well.
*/
- if ((prev_entry->inheritance == VM_INHERIT_DEFAULT) &&
+ if ((prev_entry->inheritance == inheritance) &&
(prev_entry->protection == prot) &&
(prev_entry->max_protection == max)) {
map->size += (end - prev_entry->end);
@@ -1276,7 +1281,7 @@ charged:
new_entry->offset = offset;
new_entry->avail_ssize = 0;
- new_entry->inheritance = VM_INHERIT_DEFAULT;
+ new_entry->inheritance = inheritance;
new_entry->protection = prot;
new_entry->max_protection = max;
new_entry->wired_count = 0;
diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
index 5311e02..11ff632 100644
--- a/sys/vm/vm_map.h
+++ b/sys/vm/vm_map.h
@@ -307,7 +307,7 @@ long vmspace_wired_count(struct vmspace *vmspace);
/*
* Copy-on-write flags for vm_map operations
*/
-#define MAP_UNUSED_01 0x0001
+#define MAP_INHERIT_SHARE 0x0001
#define MAP_COPY_ON_WRITE 0x0002
#define MAP_NOFAULT 0x0004
#define MAP_PREFAULT 0x0008
diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
index e85b681..4b4996f 100644
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -1517,6 +1517,9 @@ vm_mmap(vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot,
docow |= MAP_DISABLE_SYNCER;
if (flags & MAP_NOCORE)
docow |= MAP_DISABLE_COREDUMP;
+ /* Shared memory is also shared with children. */
+ if (flags & MAP_SHARED)
+ docow |= MAP_INHERIT_SHARE;
if (flags & MAP_STACK)
rv = vm_map_stack(map, *addr, size, prot, maxprot,
@@ -1536,13 +1539,6 @@ vm_mmap(vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot,
* or named anonymous without other references.
*/
vm_object_deallocate(object);
- } else if (flags & MAP_SHARED) {
- /*
- * Shared memory is also shared with children.
- */
- rv = vm_map_inherit(map, *addr, *addr + size, VM_INHERIT_SHARE);
- if (rv != KERN_SUCCESS)
- (void) vm_map_remove(map, *addr, *addr + size);
}
/*
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