Based on commit 1091458d09e1a (mmap randomization)
For 32-bit address spaces randomize within a
16MB space, for 64-bit within a 256MB space.
Test Results:
------------
Without Patch (VDSO is not randomized)
---------------------------------------
root@Maleo:~# ./aslr vdso
FAIL: ASLR not functional (vdso always at 0x7fff7000)
root@Maleo:~# ./aslr rekey vdso
pre_val==cur_val
value=0x7fff7000
With patch:(VDSO is randmoized and doesn't interfere with stack)
----------------------------------------------------------------
root@cavium-octeon2:~# ./aslr rekey vdso
pre_val!=cur_val
previous_value=0x7f830ea2
current_value=0x776e2000
root@cavium-octeon2:~# ./aslr rekey vdso
pre_val!=cur_val
previous_value=0x7fb0cea2
current_value=0x77209000
root@cavium-octeon2:~# ./aslr rekey vdso
pre_val!=cur_val
previous_value=0x7f985ea2
current_value=0x7770c000
root@cavium-octeon2:~# ./aslr rekey vdso
pre_val!=cur_val
previous_value=0x7fbc6ea2
current_value=0x7fe25000
Maps file output:
-------------------------
root@cavium-octeon2:~# ./aslr rekey maps
78584000-785a5000 rwxp 00000000 00:00 0 [heap]
7f9d0000-7f9f1000 rw-p 00000000 00:00 0 [stack]
7ffa5000-7ffa6000 r-xp 00000000 00:00 0 [vdso]
root@cavium-octeon2:~# ./aslr rekey maps
77de0000-77e01000 rwxp 00000000 00:00 0 [heap]
7f91b000-7f93c000 rw-p 00000000 00:00 0 [stack]
7ff99000-7ff9a000 r-xp 00000000 00:00 0 [vdso]
root@cavium-octeon2:~# ./aslr rekey maps
77d7f000-77da0000 rwxp 00000000 00:00 0 [heap]
7fc2a000-7fc4b000 rw-p 00000000 00:00 0 [stack]
7fe09000-7fe0a000 r-xp 00000000 00:00 0 [vdso]
root@cavium-octeon2:~# ./aslr rekey maps
7794c000-7794d000 r-xp 00000000 00:00 0 [vdso]
77e4b000-77e6c000 rwxp 00000000 00:00 0 [heap]
7f6e7000-7f708000 rw-p 00000000 00:00 0 [stack]
root@cavium-octeon2:~#
Signed-off-by: Prem Karat <pkarat@xxxxxxxxxx>
---
arch/mips/kernel/vdso.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
index 0f1af58..ed2a278 100644
--- a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -16,9 +16,11 @@
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/unistd.h>
+#include <linux/random.h>
#include <asm/vdso.h>
#include <asm/uasm.h>
+#include <asm/processor.h>
/*
* Including <asm/unistd.h> would give use the 64-bit syscall numbers ...
@@ -67,7 +69,18 @@ subsys_initcall(init_vdso);
static unsigned long vdso_addr(unsigned long start)
{
- return STACK_TOP;
+ unsigned long offset = 0UL;
+
+ if (current->flags & PF_RANDOMIZE) {
+ offset = get_random_int();
+ offset <<= PAGE_SHIFT;
+ if (TASK_IS_32BIT_ADDR)
+ offset &= 0xfffffful;
+ else
+ offset &= 0xffffffful;
+ }
+
+ return STACK_TOP + offset;
}
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
--
1.7.9.5
