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powerpc/mm: Fix kernel RAM protection after freeing unused memory on PPC32

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As seen below, allthough the init sections have been freed, the
associated memory area is still marked as executable in the
page tables.

~ dmesg
[    5.860093] Freeing unused kernel memory: 592K (c0570000 - c0604000)

~ cat /sys/kernel/debug/kernel_page_tables
---[ Start of kernel VM ]---
0xc0000000-0xc0497fff        4704K  rw  X  present dirty accessed shared
0xc0498000-0xc056ffff         864K  rw     present dirty accessed shared
0xc0570000-0xc059ffff         192K  rw  X  present dirty accessed shared
0xc05a0000-0xc7ffffff      125312K  rw     present dirty accessed shared
---[ vmalloc() Area ]---

This patch fixes that.

The implementation is done by reusing the change_page_attr()
function implemented for CONFIG_DEBUG_PAGEALLOC

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2017-08-02 15:51:03 +02:00 committed by Michael Ellerman
parent e611939fc8
commit 3184cc4b6f
2 changed files with 11 additions and 4 deletions
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2
arch/powerpc/include/asm/pgtable.h
View File

@ -81,7 +81,7 @@ unsigned long vmalloc_to_phys(void *vmalloc_addr);
void pgtable_cache_add(unsigned shift, void (*ctor)(void *));
void pgtable_cache_init(void);
#ifdef CONFIG_STRICT_KERNEL_RWX
#if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_PPC32)
void mark_initmem_nx(void);
#else
static inline void mark_initmem_nx(void) { }

13
arch/powerpc/mm/pgtable_32.c
View File

@ -323,8 +323,6 @@ get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
return(retval);
}
#ifdef CONFIG_DEBUG_PAGEALLOC
static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
{
pte_t *kpte;
@ -347,7 +345,7 @@ static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
/*
* Change the page attributes of an page in the linear mapping.
*
* THIS CONFLICTS WITH BAT MAPPINGS, DEBUG USE ONLY
* THIS DOES NOTHING WITH BAT MAPPINGS, DEBUG USE ONLY
*/
static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
{
@ -368,7 +366,16 @@ static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
return err;
}
void mark_initmem_nx(void)
{
struct page *page = virt_to_page(_sinittext);
unsigned long numpages = PFN_UP((unsigned long)_einittext) -
PFN_DOWN((unsigned long)_sinittext);
change_page_attr(page, numpages, PAGE_KERNEL);
}
#ifdef CONFIG_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable)
{
if (PageHighMem(page))