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authorRusty Russell <rusty@rustcorp.com.au>2013-04-22 14:10:37 +0930
committerRusty Russell <rusty@rustcorp.com.au>2013-04-22 15:31:34 +0930
commit68a644d734e61f38b686cb755bd2a3f43d9372f4 (patch)
treeea2e4f575463a080cbd426338f3666852ea8919d /drivers/lguest
parent406a590ba105bfb7b67952f0a5f948e0d374e03e (diff)
downloadkernel-68a644d734e61f38b686cb755bd2a3f43d9372f4.tar.gz
lguest: check vaddr not pgd for Switcher protection.
We currently assume that the Switcher the top pgd; we want to remove this assumption, so check that vaddr is OK, rather then checking pgd index. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers/lguest')
-rw-r--r--drivers/lguest/page_tables.c37
1 files changed, 16 insertions, 21 deletions
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index 3b62be160a6e..a2454a24a10c 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -95,13 +95,6 @@ static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr)
{
unsigned int index = pgd_index(vaddr);
-#ifndef CONFIG_X86_PAE
- /* We kill any Guest trying to touch the Switcher addresses. */
- if (index >= SWITCHER_PGD_INDEX) {
- kill_guest(cpu, "attempt to access switcher pages");
- index = 0;
- }
-#endif
/* Return a pointer index'th pgd entry for the i'th page table. */
return &cpu->lg->pgdirs[i].pgdir[index];
}
@@ -117,13 +110,6 @@ static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
unsigned int index = pmd_index(vaddr);
pmd_t *page;
- /* We kill any Guest trying to touch the Switcher addresses. */
- if (pgd_index(vaddr) == SWITCHER_PGD_INDEX &&
- index >= SWITCHER_PMD_INDEX) {
- kill_guest(cpu, "attempt to access switcher pages");
- index = 0;
- }
-
/* You should never call this if the PGD entry wasn't valid */
BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT));
page = __va(pgd_pfn(spgd) << PAGE_SHIFT);
@@ -323,6 +309,10 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
pmd_t gpmd;
#endif
+ /* We never demand page the Switcher, so trying is a mistake. */
+ if (vaddr >= switcher_addr)
+ return false;
+
/* First step: get the top-level Guest page table entry. */
if (unlikely(cpu->linear_pages)) {
/* Faking up a linear mapping. */
@@ -495,10 +485,14 @@ static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr)
{
pgd_t *spgd;
unsigned long flags;
-
#ifdef CONFIG_X86_PAE
pmd_t *spmd;
#endif
+
+ /* You can't put your stack in the Switcher! */
+ if (vaddr >= switcher_addr)
+ return false;
+
/* Look at the current top level entry: is it present? */
spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
if (!(pgd_flags(*spgd) & _PAGE_PRESENT))
@@ -897,6 +891,12 @@ static void do_set_pte(struct lg_cpu *cpu, int idx,
void guest_set_pte(struct lg_cpu *cpu,
unsigned long gpgdir, unsigned long vaddr, pte_t gpte)
{
+ /* We don't let you remap the Switcher; we need it to get back! */
+ if (vaddr >= switcher_addr) {
+ kill_guest(cpu, "attempt to set pte into Switcher pages");
+ return;
+ }
+
/*
* Kernel mappings must be changed on all top levels. Slow, but doesn't
* happen often.
@@ -995,12 +995,7 @@ void page_table_guest_data_init(struct lg_cpu *cpu)
* "pgd_index(lg->kernel_address)". This assumes it won't hit the
* Switcher mappings, so check that now.
*/
-#ifdef CONFIG_X86_PAE
- if (pgd_index(cpu->lg->kernel_address) == SWITCHER_PGD_INDEX &&
- pmd_index(cpu->lg->kernel_address) == SWITCHER_PMD_INDEX)
-#else
- if (pgd_index(cpu->lg->kernel_address) >= SWITCHER_PGD_INDEX)
-#endif
+ if (cpu->lg->kernel_address >= switcher_addr)
kill_guest(cpu, "bad kernel address %#lx",
cpu->lg->kernel_address);
}