On Fri, 23 Mar 2001, Adam J. Richter wrote:
>
> In linux-2.4.3-pre6, a call to vmalloc can result in a call to
> pte_alloc without the appropriate page_table_lock being held. Here is
> the call graph, from my post of about half an hour ago:
Good find.
HOWEVER, the patch is not right.
You cannot get the kernel lock from within a spinlock, so you should
_replace_ the kernel lock with the spinlock (which is definitely the
correct thing to do anyway - the kernel lock is there exactly because we
didn't have any other good synchronization primitive, and that's _exactly_
what the spinlock in question is all about).
Also, you have to drop the spinlock over the actual page allocation inside
alloc_area_pte(). So I'd suggest something along the lines of the attached
(completely untested) patch.
Linus
-----
--- pre6/linux/mm/vmalloc.c Tue Mar 20 23:13:03 2001
+++ linux/mm/vmalloc.c Fri Mar 23 11:38:24 2001
@@ -102,9 +102,11 @@
end = PMD_SIZE;
do {
struct page * page;
+ spin_unlock(&init_mm.page_table_lock);
+ page = alloc_page(gfp_mask);
+ spin_lock(&init_mm.page_table_lock);
if (!pte_none(*pte))
printk(KERN_ERR "alloc_area_pte: page already exists\n");
- page = alloc_page(gfp_mask);
if (!page)
return -ENOMEM;
set_pte(pte, mk_pte(page, prot));
@@ -143,7 +145,7 @@
dir = pgd_offset_k(address);
flush_cache_all();
- lock_kernel();
+ spin_lock(&init_mm.page_table_lock);
do {
pmd_t *pmd;
@@ -161,7 +163,7 @@
ret = 0;
} while (address && (address < end));
- unlock_kernel();
+ spin_unlock(&init_mm.page_table_lock)
flush_tlb_all();
return ret;
}
-
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