Fix a race condition regarding allocating/freeing memory.

Taogle2018 · Taogle2018 · commit 1b98f47a478f · 2020-08-04T15:49:55.000-07:00
diff --git a/ntkrutils.h b/ntkrutils.h
@@ -869,12 +869,11 @@ static __inline struct page *alloc_page(unsigned int gfp_mask)
 
 static __inline void __free_pages(struct page* page, unsigned int order)
 {
-	ExFreePoolWithTag(page->hva, GVM_POOL_TAG);
-
 	raw_spin_lock(&global_page_lock);
 	pglist[page->pfn] = 0;
 	raw_spin_unlock(&global_page_lock);
 
+	ExFreePoolWithTag(page->hva, GVM_POOL_TAG);
 	ExFreePoolWithTag(page, GVM_POOL_TAG);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -869,12 +869,11 @@ static __inline struct page *alloc_page(unsigned int gfp_mask)`
`869`	`869`
`870`	`870`	`static __inline void __free_pages(struct page* page, unsigned int order)`
`871`	`871`	`{`
`872`		`- ExFreePoolWithTag(page->hva, GVM_POOL_TAG);`
`873`		`-`
`874`	`872`	`raw_spin_lock(&global_page_lock);`
`875`	`873`	`pglist[page->pfn] = 0;`
`876`	`874`	`raw_spin_unlock(&global_page_lock);`
`877`	`875`
	`876`	`+ ExFreePoolWithTag(page->hva, GVM_POOL_TAG);`
`878`	`877`	`ExFreePoolWithTag(page, GVM_POOL_TAG);`
`879`	`878`	`}`
`880`	`879`