[PATCH v7u1 30/31] x86, 64bit, mm: Mark data/bss/brk to nx

From: Yinghai Lu
Date: Thu Jan 03 2013 - 19:51:01 EST


HPA said, we should not have RW and +x set at the time.

for kernel layout:
[ 0.000000] Kernel Layout:
[ 0.000000] .text: [0x01000000-0x021434f8]
[ 0.000000] .rodata: [0x02200000-0x02a13fff]
[ 0.000000] .data: [0x02c00000-0x02dc763f]
[ 0.000000] .init: [0x02dc9000-0x0312cfff]
[ 0.000000] .bss: [0x0313b000-0x03dd6fff]
[ 0.000000] .brk: [0x03dd7000-0x03dfffff]

before the patch, we have
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffff81000000 16M pmd
0xffffffff81000000-0xffffffff82200000 18M ro PSE GLB x pmd
0xffffffff82200000-0xffffffff82c00000 10M ro PSE GLB NX pmd
0xffffffff82c00000-0xffffffff82dc9000 1828K RW GLB x pte
0xffffffff82dc9000-0xffffffff82e00000 220K RW GLB NX pte
0xffffffff82e00000-0xffffffff83000000 2M RW PSE GLB NX pmd
0xffffffff83000000-0xffffffff8313a000 1256K RW GLB NX pte
0xffffffff8313a000-0xffffffff83200000 792K RW GLB x pte
0xffffffff83200000-0xffffffff83e00000 12M RW PSE GLB x pmd
0xffffffff83e00000-0xffffffffa0000000 450M pmd

after patch,, we get
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffff81000000 16M pmd
0xffffffff81000000-0xffffffff82200000 18M ro PSE GLB x pmd
0xffffffff82200000-0xffffffff82c00000 10M ro PSE GLB NX pmd
0xffffffff82c00000-0xffffffff82e00000 2M RW GLB NX pte
0xffffffff82e00000-0xffffffff83000000 2M RW PSE GLB NX pmd
0xffffffff83000000-0xffffffff83200000 2M RW GLB NX pte
0xffffffff83200000-0xffffffff83e00000 12M RW PSE GLB NX pmd
0xffffffff83e00000-0xffffffffa0000000 450M pmd

so data, bss, brk get NX ...

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
arch/x86/mm/init_64.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 98385a2..9653411 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -820,6 +820,7 @@ void mark_rodata_ro(void)
unsigned long end = (unsigned long) &__end_rodata_hpage_align;
unsigned long text_end = PFN_ALIGN(&__stop___ex_table);
unsigned long rodata_end = PFN_ALIGN(&__end_rodata);
+ unsigned long all_end = PFN_ALIGN(&_end);

printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
(end - start) >> 10);
@@ -828,10 +829,10 @@ void mark_rodata_ro(void)
kernel_set_to_readonly = 1;

/*
- * The rodata section (but not the kernel text!) should also be
- * not-executable.
+ * The rodata/data/bss/brk section (but not the kernel text!)
+ * should also be not-executable.
*/
- set_memory_nx(rodata_start, (end - rodata_start) >> PAGE_SHIFT);
+ set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT);

rodata_test();

--
1.7.10.4

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