Commit 41cd81ab authored by Sven Schnelle's avatar Sven Schnelle Committed by Heiko Carstens
Browse files

s390/vdso: add vdso randomization 



Randomize the address of vdso if randomize_va_space is enabled.
Note that this keeps the vdso address on the same PMD as the stack
to avoid allocating an extra page table just for vdso.

Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 9e37a2e8

arch/s390/kernel/vdso.c

+32 −1
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/slab.h>

#include <linux/smp.h>

#include <linux/time_namespace.h>

#include <linux/random.h>

#include <vdso/datapage.h>

#include <asm/vdso.h>
@@ -208,6 +209,31 @@ static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len) 
	return rc;

}



static unsigned long vdso_addr(unsigned long start, unsigned long len)

{

	unsigned long addr, end, offset;



	/*

	 * Round up the start address. It can start out unaligned as a result

	 * of stack start randomization.

	 */

	start = PAGE_ALIGN(start);



	/* Round the lowest possible end address up to a PMD boundary. */

	end = (start + len + PMD_SIZE - 1) & PMD_MASK;

	if (end >= VDSO_BASE)

		end = VDSO_BASE;

	end -= len;



	if (end > start) {

		offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);

		addr = start + (offset << PAGE_SHIFT);

	} else {

		addr = start;

	}

	return addr;

}



unsigned long vdso_size(void)

{

	unsigned long size = VVAR_NR_PAGES * PAGE_SIZE;
@@ -221,7 +247,12 @@ unsigned long vdso_size(void) 


int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

{

	return map_vdso(VDSO_BASE, vdso_size());

	unsigned long addr = VDSO_BASE;

	unsigned long size = vdso_size();



	if (current->flags & PF_RANDOMIZE)

		addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size);

	return map_vdso(addr, size);

}



static struct page ** __init vdso_setup_pages(void *start, void *end)