* [PATCH] powerpc/32: Fix protection of kernel RAM after freeing unused memory
@ 2017-04-14 13:11 Christophe Leroy
2017-04-18 6:40 ` Michael Ellerman
0 siblings, 1 reply; 3+ messages in thread
From: Christophe Leroy @ 2017-04-14 13:11 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, Scott Wood
Cc: linux-kernel, linuxppc-dev
As seen below, allthough the init sections have been freed, the
associated memory area is still marked as executable in the
page tables. This patch fixes that.
[ 5.860093] Freeing unused kernel memory: 592K (c0570000 - c0604000)
---[ 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 ]---
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/mm/mem.c | 3 +++
arch/powerpc/mm/mmu_decl.h | 1 +
arch/powerpc/mm/pgtable_32.c | 20 ++++++++++++++++++++
3 files changed, 24 insertions(+)
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 9ee536ec0739..e95931c4e6cf 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -401,6 +401,9 @@ void free_initmem(void)
{
ppc_md.progress = ppc_printk_progress;
free_initmem_default(POISON_FREE_INITMEM);
+#ifdef CONFIG_PPC32
+ remap_init_ram();
+#endif
}
#ifdef CONFIG_BLK_DEV_INITRD
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index f988db655e5b..d39d92600839 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -95,6 +95,7 @@ extern void _tlbia(void);
extern void mapin_ram(void);
extern int map_page(unsigned long va, phys_addr_t pa, int flags);
+void remap_init_ram(void);
extern void setbat(int index, unsigned long virt, phys_addr_t phys,
unsigned int size, pgprot_t prot);
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index a65c0b4c0669..d506bd61b629 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -323,6 +323,26 @@ get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
return(retval);
}
+void remap_init_ram(void)
+{
+ unsigned long start = (unsigned long)_sinittext & PAGE_MASK;
+ unsigned long end = (unsigned long)_einittext;
+ unsigned long va;
+
+ for (va = start; va < end; va += PAGE_SIZE) {
+ pte_t *kpte;
+ pmd_t *kpmd;
+ pte_t pte = pfn_pte(__pa(va) >> PAGE_SHIFT, PAGE_KERNEL);
+
+ if (!get_pteptr(&init_mm, va, &kpte, &kpmd))
+ continue;
+ __set_pte_at(&init_mm, va, kpte, pte, 0);
+ wmb();
+ pte_unmap(kpte);
+ }
+ flush_tlb_kernel_range(start, end);
+}
+
#ifdef CONFIG_DEBUG_PAGEALLOC
static int __change_page_attr(struct page *page, pgprot_t prot)
--
2.12.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] powerpc/32: Fix protection of kernel RAM after freeing unused memory
2017-04-14 13:11 [PATCH] powerpc/32: Fix protection of kernel RAM after freeing unused memory Christophe Leroy
@ 2017-04-18 6:40 ` Michael Ellerman
2017-04-18 8:15 ` Christophe LEROY
0 siblings, 1 reply; 3+ messages in thread
From: Michael Ellerman @ 2017-04-18 6:40 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras, Scott Wood
Cc: linux-kernel, linuxppc-dev
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index 9ee536ec0739..e95931c4e6cf 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -401,6 +401,9 @@ void free_initmem(void)
> {
> ppc_md.progress = ppc_printk_progress;
> free_initmem_default(POISON_FREE_INITMEM);
> +#ifdef CONFIG_PPC32
> + remap_init_ram();
> +#endif
> }
Please don't put ifdefs straight in C code like that unless you have to.
In this case it's easy to put an empty version in a header, eg:
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index f988db655e5b..d39d92600839 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -95,6 +95,7 @@ extern void _tlbia(void);
>
> extern void mapin_ram(void);
> extern int map_page(unsigned long va, phys_addr_t pa, int flags);
+#ifdef CONFIG_PPC32
> +void remap_init_ram(void);
+#else
+static inline void remap_init_ram(void) { }
+#endif
> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
> index a65c0b4c0669..d506bd61b629 100644
> --- a/arch/powerpc/mm/pgtable_32.c
> +++ b/arch/powerpc/mm/pgtable_32.c
> @@ -323,6 +323,26 @@ get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
> return(retval);
> }
>
> +void remap_init_ram(void)
> +{
> + unsigned long start = (unsigned long)_sinittext & PAGE_MASK;
> + unsigned long end = (unsigned long)_einittext;
> + unsigned long va;
> +
> + for (va = start; va < end; va += PAGE_SIZE) {
> + pte_t *kpte;
> + pmd_t *kpmd;
> + pte_t pte = pfn_pte(__pa(va) >> PAGE_SHIFT, PAGE_KERNEL);
> +
> + if (!get_pteptr(&init_mm, va, &kpte, &kpmd))
> + continue;
> + __set_pte_at(&init_mm, va, kpte, pte, 0);
> + wmb();
> + pte_unmap(kpte);
> + }
> + flush_tlb_kernel_range(start, end);
> +}
Can we just use unmap_kernel_range() ?
Is this sufficient on all 32-bit PPC? (I have no idea)
cheers
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] powerpc/32: Fix protection of kernel RAM after freeing unused memory
2017-04-18 6:40 ` Michael Ellerman
@ 2017-04-18 8:15 ` Christophe LEROY
0 siblings, 0 replies; 3+ messages in thread
From: Christophe LEROY @ 2017-04-18 8:15 UTC (permalink / raw)
To: Michael Ellerman, Benjamin Herrenschmidt, Paul Mackerras, Scott Wood
Cc: linux-kernel, linuxppc-dev
Le 18/04/2017 à 08:40, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>
>
>> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
>> index a65c0b4c0669..d506bd61b629 100644
>> --- a/arch/powerpc/mm/pgtable_32.c
>> +++ b/arch/powerpc/mm/pgtable_32.c
>> @@ -323,6 +323,26 @@ get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
>> return(retval);
>> }
>>
>> +void remap_init_ram(void)
>> +{
>> + unsigned long start = (unsigned long)_sinittext & PAGE_MASK;
>> + unsigned long end = (unsigned long)_einittext;
>> + unsigned long va;
>> +
>> + for (va = start; va < end; va += PAGE_SIZE) {
>> + pte_t *kpte;
>> + pmd_t *kpmd;
>> + pte_t pte = pfn_pte(__pa(va) >> PAGE_SHIFT, PAGE_KERNEL);
>> +
>> + if (!get_pteptr(&init_mm, va, &kpte, &kpmd))
>> + continue;
>> + __set_pte_at(&init_mm, va, kpte, pte, 0);
>> + wmb();
>> + pte_unmap(kpte);
>> + }
>> + flush_tlb_kernel_range(start, end);
>> +}
>
> Can we just use unmap_kernel_range() ?
We only want to remove the X bit.
I think unmap_kernel_range() will unmap the area, wheareas we want to
keep it as part of the linear data area.
Christophe
>
> Is this sufficient on all 32-bit PPC? (I have no idea)
>
> cheers
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-04-14 13:11 [PATCH] powerpc/32: Fix protection of kernel RAM after freeing unused memory Christophe Leroy
2017-04-18 6:40 ` Michael Ellerman
2017-04-18 8:15 ` Christophe LEROY
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