Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 68a644d7 authored by Rusty Russell's avatar Rusty Russell
Browse files

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: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 406a590b

drivers/lguest/page_tables.c

+16 −21
Original line number Diff line number Diff line
@@ -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);

}