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Subject[PATCHv2] arm: Update all mm structures with section adjustments
Date
Currently, when updating section permissions to mark areas RO
or NX, the only mm updated is current->mm. This is working off
the assumption that there are no additional mm structures at
the time. This may not always hold true. (Example: calling
modprobe early will trigger a fork/exec). Ensure all mm structres
get updated with the new section information.

Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
---
I don't think we can get away from updating the sections if the initmem is
going to be freed back to the buddy allocator. I think this should cover
everything based on my understanding but my knowledge may be incomplete.
---
arch/arm/mm/init.c | 92 ++++++++++++++++++++++++++++++++++++------------------
1 file changed, 62 insertions(+), 30 deletions(-)

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 8a63b4c..7f8cd1b 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -22,6 +22,7 @@
#include <linux/memblock.h>
#include <linux/dma-contiguous.h>
#include <linux/sizes.h>
+#include <linux/stop_machine.h>

#include <asm/cp15.h>
#include <asm/mach-types.h>
@@ -627,12 +628,10 @@ static struct section_perm ro_perms[] = {
* safe to be called with preemption disabled, as under stop_machine().
*/
static inline void section_update(unsigned long addr, pmdval_t mask,
- pmdval_t prot)
+ pmdval_t prot, struct mm_struct *mm)
{
- struct mm_struct *mm;
pmd_t *pmd;

- mm = current->active_mm;
pmd = pmd_offset(pud_offset(pgd_offset(mm, addr), addr), addr);

#ifdef CONFIG_ARM_LPAE
@@ -656,49 +655,82 @@ static inline bool arch_has_strict_perms(void)
return !!(get_cr() & CR_XP);
}

-#define set_section_perms(perms, field) { \
- size_t i; \
- unsigned long addr; \
- \
- if (!arch_has_strict_perms()) \
- return; \
- \
- for (i = 0; i < ARRAY_SIZE(perms); i++) { \
- if (!IS_ALIGNED(perms[i].start, SECTION_SIZE) || \
- !IS_ALIGNED(perms[i].end, SECTION_SIZE)) { \
- pr_err("BUG: section %lx-%lx not aligned to %lx\n", \
- perms[i].start, perms[i].end, \
- SECTION_SIZE); \
- continue; \
- } \
- \
- for (addr = perms[i].start; \
- addr < perms[i].end; \
- addr += SECTION_SIZE) \
- section_update(addr, perms[i].mask, \
- perms[i].field); \
- } \
+void set_section_perms(struct section_perm *perms, int n, bool set,
+ struct mm_struct *mm)
+{
+ size_t i;
+ unsigned long addr;
+
+ if (!arch_has_strict_perms())
+ return;
+
+ for (i = 0; i < n; i++) {
+ if (!IS_ALIGNED(perms[i].start, SECTION_SIZE) ||
+ !IS_ALIGNED(perms[i].end, SECTION_SIZE)) {
+ pr_err("BUG: section %lx-%lx not aligned to %lx\n",
+ perms[i].start, perms[i].end,
+ SECTION_SIZE);
+ continue;
+ }
+
+ for (addr = perms[i].start;
+ addr < perms[i].end;
+ addr += SECTION_SIZE)
+ section_update(addr, perms[i].mask,
+ set ? perms[i].prot : perms[i].clear, mm);
+ }
+
}

-static inline void fix_kernmem_perms(void)
+static void update_sections_early(struct section_perm perms[], int n)
{
- set_section_perms(nx_perms, prot);
+ struct task_struct *t, *s;
+
+ read_lock(&tasklist_lock);
+ for_each_process(t) {
+ if (t->flags & PF_KTHREAD)
+ continue;
+ for_each_thread(t, s)
+ set_section_perms(perms, n, true, s->mm);
+ }
+ read_unlock(&tasklist_lock);
+ set_section_perms(perms, n, true, current->active_mm);
+ set_section_perms(perms, n, true, &init_mm);
+}
+
+int __fix_kernmem_perms(void *unused)
+{
+ update_sections_early(nx_perms, ARRAY_SIZE(nx_perms));
+ return 0;
+}
+
+void fix_kernmem_perms(void)
+{
+ stop_machine(__fix_kernmem_perms, NULL, NULL);
}

#ifdef CONFIG_DEBUG_RODATA
+int __mark_rodata_ro(void *unused)
+{
+ update_sections_early(ro_perms, ARRAY_SIZE(ro_perms));
+ return 0;
+}
+
void mark_rodata_ro(void)
{
- set_section_perms(ro_perms, prot);
+ stop_machine(__mark_rodata_ro, NULL, NULL);
}

void set_kernel_text_rw(void)
{
- set_section_perms(ro_perms, clear);
+ set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), false,
+ current->active_mm);
}

void set_kernel_text_ro(void)
{
- set_section_perms(ro_perms, prot);
+ set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), true,
+ current->active_mm);
}
#endif /* CONFIG_DEBUG_RODATA */

--
2.5.0


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