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Close a race due to dropping of the map lock between creating map entry

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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
This commit is contained in:
Konstantin Belousov 2012-02-11 17:29:07 +00:00
parent 86b914642c
commit 8211bd45bc
3 changed files with 11 additions and 10 deletions
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9
sys/vm/vm_map.c
View File

@ -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 @@ vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
* 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 @@ vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
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;

2
sys/vm/vm_map.h
View File

@ -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

10
sys/vm/vm_mmap.c
View File

@ -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);
}
/*