fix iounmap and a pageattr memleak (x86 and x86-64)

Andrea Arcangeli
2004-10-28T19:24:17Z

This first patch fixes silent memleak in the pageattr code that I found
while searching for the bug Andi fixed in the second patch below
(basically reference counting in split page was done on the pmd instead
of the pte).

Signed-off-by: Andrea Arcangeli <andrea@novell.com>

Index: linux-2.5/arch/i386/mm/pageattr.c
===================================================================
RCS file: /home/andrea/crypto/cvs/linux-2.5/arch/i386/mm/pageattr.c,v
retrieving revision 1.13
diff -u -p -r1.13 pageattr.c
--- linux-2.5/arch/i386/mm/pageattr.c 27 Aug 2004 17:35:39 -0000 1.13
+++ linux-2.5/arch/i386/mm/pageattr.c 28 Oct 2004 19:11:20 -0000
@@ -117,22 +117,23 @@ __change_page_attr(struct page *page, pg
kpte_page = virt_to_page(kpte);
if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) {
if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
- pte_t old = *kpte;
- pte_t standard = mk_pte(page, PAGE_KERNEL);
set_pte_atomic(kpte, mk_pte(page, prot));
- if (pte_same(old,standard))
- get_page(kpte_page);
} else {
struct page *split = split_large_page(address, prot);
if (!split)
return -ENOMEM;
- get_page(kpte_page);
set_pmd_pte(kpte,address,mk_pte(split, PAGE_KERNEL));
+ kpte_page = split;
}
+ get_page(kpte_page);
} else if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
__put_page(kpte_page);
- }
+ } else
+ BUG();
+
+ /* memleak and potential failed 2M page regeneration */
+ BUG_ON(!page_count(kpte_page));

if (cpu_has_pse && (page_count(kpte_page) == 1)) {
list_add(&kpte_page->lru, &df_list);
Index: linux-2.5/arch/x86_64/mm/pageattr.c
===================================================================
RCS file: /home/andrea/crypto/cvs/linux-2.5/arch/x86_64/mm/pageattr.c,v
retrieving revision 1.12
diff -u -p -r1.12 pageattr.c
--- linux-2.5/arch/x86_64/mm/pageattr.c 27 Jun 2004 17:54:00 -0000 1.12
+++ linux-2.5/arch/x86_64/mm/pageattr.c 28 Oct 2004 19:11:20 -0000
@@ -124,28 +124,33 @@ __change_page_attr(unsigned long address
kpte_flags = pte_val(*kpte);
if (pgprot_val(prot) != pgprot_val(ref_prot)) {
if ((kpte_flags & _PAGE_PSE) == 0) {
- pte_t old = *kpte;
- pte_t standard = mk_pte(page, ref_prot);
-
set_pte(kpte, mk_pte(page, prot));
- if (pte_same(old,standard))
- get_page(kpte_page);
} else {
+ /*
+ * split_large_page will take the reference for this change_page_attr
+ * on the split page.
+ */
struct page *split = split_large_page(address, prot, ref_prot);
if (!split)
return -ENOMEM;
- get_page(kpte_page);
set_pte(kpte,mk_pte(split, ref_prot));
+ kpte_page = split;
}
+ get_page(kpte_page);
} else if ((kpte_flags & _PAGE_PSE) == 0) {
set_pte(kpte, mk_pte(page, ref_prot));
__put_page(kpte_page);
- }
+ } else
+ BUG();

- if (page_count(kpte_page) == 1) {
+ switch (page_count(kpte_page)) {
+ case 1:
save_page(address, kpte_page);
revert_page(address, ref_prot);
- }
+ break;
+ case 0:
+ BUG(); /* memleak and failed 2M page regeneration */
+ }
return 0;
}

This below patch from Andi is also needed to make the above work on x86
(otherwise one of my new above BUGS() will trigger signalling the fact
a bug was there). The below patch creates a subtle dependency that
(_PAGE_PCD << 24) must not be zero. It's not the cleanest thing ever,
but since it's an hardware bitflag I doubt it's going to break.

I'm not sure if I'm allowed to add the signedoff for Andi but I think I
should since he wrote the x86-64 version, if not please let me know (I
only backported it to x86 to test my above changes that otherwise would
trigger one of my added BUGs, and I did the other worthless cosmetical
fixes).

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrea Arcangeli <andrea@novell.com>

Index: linux-2.5/arch/i386/mm/ioremap.c
===================================================================
RCS file: /home/andrea/crypto/cvs/linux-2.5/arch/i386/mm/ioremap.c,v
retrieving revision 1.23
diff -u -p -r1.23 ioremap.c
--- linux-2.5/arch/i386/mm/ioremap.c 11 Sep 2004 02:01:36 -0000 1.23
+++ linux-2.5/arch/i386/mm/ioremap.c 28 Oct 2004 19:11:20 -0000
@@ -152,7 +152,7 @@ void __iomem * __ioremap(unsigned long p
/*
* Ok, go for it..
*/
- area = get_vm_area(size, VM_IOREMAP);
+ area = get_vm_area(size, VM_IOREMAP | (flags << 24));
if (!area)
return NULL;
area->phys_addr = phys_addr;
@@ -232,7 +232,7 @@ void iounmap(volatile void __iomem *addr
return;
}

- if (p->flags && p->phys_addr < virt_to_phys(high_memory)) {
+ if ((p->flags >> 24) && p->phys_addr < virt_to_phys(high_memory)) {
change_page_attr(virt_to_page(__va(p->phys_addr)),
p->size >> PAGE_SHIFT,
PAGE_KERNEL);
Index: linux-2.5/arch/x86_64/mm/ioremap.c
===================================================================
RCS file: /home/andrea/crypto/cvs/linux-2.5/arch/x86_64/mm/ioremap.c,v
retrieving revision 1.16
diff -u -p -r1.16 ioremap.c
--- linux-2.5/arch/x86_64/mm/ioremap.c 22 Oct 2004 15:01:03 -0000 1.16
+++ linux-2.5/arch/x86_64/mm/ioremap.c 28 Oct 2004 19:11:20 -0000
@@ -128,11 +128,11 @@ void __iomem * __ioremap(unsigned long p
if (phys_addr >= 0xA0000 && last_addr < 0x100000)
return (__force void __iomem *)phys_to_virt(phys_addr);

+#ifndef CONFIG_DISCONTIGMEM
/*
* Don't allow anybody to remap normal RAM that we're using..
*/
if (phys_addr < virt_to_phys(high_memory)) {
-#ifndef CONFIG_DISCONTIGMEM
char *t_addr, *t_end;
struct page *page;

@@ -142,8 +142,8 @@ void __iomem * __ioremap(unsigned long p
for(page = virt_to_page(t_addr); page <= virt_to_page(t_end); page++)
if(!PageReserved(page))
return NULL;
-#endif
}
+#endif

/*
* Mappings have to be page-aligned
@@ -155,7 +155,7 @@ void __iomem * __ioremap(unsigned long p
/*
* Ok, go for it..
*/
- area = get_vm_area(size, VM_IOREMAP);
+ area = get_vm_area(size, VM_IOREMAP | (flags << 24));
if (!area)
return NULL;
area->phys_addr = phys_addr;
@@ -195,12 +195,12 @@ void __iomem *ioremap_nocache (unsigned
if (!p)
return p;

- if (phys_addr + size < virt_to_phys(high_memory)) {
+ if (phys_addr + size - 1 < virt_to_phys(high_memory)) {
struct page *ppage = virt_to_page(__va(phys_addr));
unsigned long npages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;

- BUG_ON(phys_addr+size > (unsigned long)high_memory);
- BUG_ON(phys_addr + size < phys_addr);
+ BUG_ON(phys_addr+size >= (unsigned long)high_memory);
+ BUG_ON(phys_addr + size <= phys_addr);

if (change_page_attr(ppage, npages, PAGE_KERNEL_NOCACHE) < 0) {
iounmap(p);
@@ -223,7 +223,7 @@ void iounmap(volatile void __iomem *addr
return;
}

- if (p->flags && p->phys_addr < virt_to_phys(high_memory)) {
+ if ((p->flags >> 24) && p->phys_addr + p->size < virt_to_phys(high_memory)) {
change_page_attr(virt_to_page(__va(p->phys_addr)),
p->size >> PAGE_SHIFT,
PAGE_KERNEL);

If you give them some beating on -mm let me know if you've any problem.
(running with this stuff on my machines right now, so far so good)