Commit 3184cc4b authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

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



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: default avatarChristophe Leroy <christophe.leroy@c-s.fr>

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent e611939f

arch/powerpc/include/asm/pgtable.h

+1 −1
Original line number Diff line number Diff line
@@ -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) { }

arch/powerpc/mm/pgtable_32.c

+10 −3
Original line number Diff line number Diff line
@@ -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))

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