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Fix a race in the device pager allocation. If another thread won and

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allocated the device pager for the given handle, then the object
fictitious pages list and the object membership in the global object
list still need to be initialized. Otherwise, dev_pager_dealloc() will
traverse uninitialized pointers.

Reported and tested by: pho
Reviewed by:    jhb
Approved by:	re (kensmith)
MFC after:      1 week
This commit is contained in:
Konstantin Belousov 2011-07-30 14:13:57 +00:00
parent 889dffba25
commit 339772b003
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=224522
1 changed files with 9 additions and 2 deletions
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11
sys/vm/device_pager.c
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@ -147,6 +147,7 @@ dev_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
object1 = vm_object_allocate(OBJT_DEVICE, pindex);
object1->flags |= OBJ_COLORED;
object1->pg_color = atop(paddr) - OFF_TO_IDX(off - PAGE_SIZE);
TAILQ_INIT(&object1->un_pager.devp.devp_pglist);
mtx_lock(&dev_pager_mtx);
object = vm_pager_object_lookup(&dev_pager_object_list, handle);
if (object != NULL) {
@ -159,7 +160,6 @@ dev_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
object = object1;
object1 = NULL;
object->handle = handle;
TAILQ_INIT(&object->un_pager.devp.devp_pglist);
TAILQ_INSERT_TAIL(&dev_pager_object_list, object,
pager_object_list);
}
@ -169,7 +169,14 @@ dev_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
}
mtx_unlock(&dev_pager_mtx);
dev_relthread(dev, ref);
vm_object_deallocate(object1);
if (object1 != NULL) {
object1->handle = object1;
mtx_lock(&dev_pager_mtx);
TAILQ_INSERT_TAIL(&dev_pager_object_list, object1,
pager_object_list);
mtx_unlock(&dev_pager_mtx);
vm_object_deallocate(object1);
}
return (object);
}