[PATCH v2 07/10] x86-64: Fill unused parts of the vsyscall page with 0xcc

Andy Lutomirski
2011-05-30T03:49:47Z

Jumping to 0x00 might do something depending on the following bytes.
Jumping to 0xcc is a trap. So fill the unused parts of the vsyscall
page with 0xcc to make it useless for exploits to jump there.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
---
arch/x86/kernel/vmlinux.lds.S | 16 +++++++---------
1 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 1583238..8d6a0b7 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -166,22 +166,20 @@ SECTIONS
__vsyscall_0 = .;

. = VSYSCALL_ADDR;
- .vsyscall_0 : AT(VLOAD(.vsyscall_0)) {
+ .vsyscall : AT(VLOAD(.vsyscall)) {
*(.vsyscall_0)
- } :user

- . = ALIGN(L1_CACHE_BYTES);
- .vsyscall_fn : AT(VLOAD(.vsyscall_fn)) {
+ . = ALIGN(L1_CACHE_BYTES);
*(.vsyscall_fn)
- }

- .vsyscall_1 ADDR(.vsyscall_0) + 1024: AT(VLOAD(.vsyscall_1)) {
+ . = 1024;
*(.vsyscall_1)
- }
- .vsyscall_2 ADDR(.vsyscall_0) + 2048: AT(VLOAD(.vsyscall_2)) {
+
+ . = 2048;
*(.vsyscall_2)
- }

+ . = 4096; /* Pad the whole page. */
+ } :user =0xcc
. = ALIGN(__vsyscall_0 + PAGE_SIZE, PAGE_SIZE);

#undef VSYSCALL_ADDR
--
1.7.5.1