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Subject[tip:x86/vdso] x86-64: Fill unused parts of the vsyscall page with 0xcc
Commit-ID:  5dfcea629a08b4684a019cd0cb59d0c9129a6c02
Gitweb: http://git.kernel.org/tip/5dfcea629a08b4684a019cd0cb59d0c9129a6c02
Author: Andy Lutomirski <luto@MIT.EDU>
AuthorDate: Sun, 5 Jun 2011 13:50:23 -0400
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 6 Jun 2011 09:43:14 +0200

x86-64: Fill unused parts of the vsyscall page with 0xcc

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>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: richard -rw- weinberger <richard.weinberger@gmail.com>
Cc: Mikael Pettersson <mikpe@it.uu.se>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: Valdis.Kletnieks@vt.edu
Cc: pageexec@freemail.hu
Link: http://lkml.kernel.org/r/ed54bfcfbe50a9070d20ec1edbe0d149e22a4568.1307292171.git.luto@mit.edu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
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 4f90082..8017471 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

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