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x86-64: Give vvars their own page

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Move vvars out of the vsyscall page into their own page and mark
it NX.

Without this patch, an attacker who can force a daemon to call
some fixed address could wait until the time contains, say,
0xCD80, and then execute the current time.

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/b1460f81dc4463d66ea3f2b5ce240f58d48effec.1307292171.git.luto@mit.edu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Andy Lutomirski
2011-06-05 13:50:19 -04:00
committed by Ingo Molnar
parent 8b4777a4b5
commit 9fd67b4ed0
5 changed files with 35 additions and 23 deletions
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22
arch/x86/include/asm/vvar.h
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@ -10,15 +10,14 @@
* In normal kernel code, they are used like any other variable.
* In user code, they are accessed through the VVAR macro.
*
* Each of these variables lives in the vsyscall page, and each
* one needs a unique offset within the little piece of the page
* reserved for vvars. Specify that offset in DECLARE_VVAR.
* (There are 896 bytes available. If you mess up, the linker will
* catch it.)
* These variables live in a page of kernel data that has an extra RO
* mapping for userspace. Each variable needs a unique offset within
* that page; specify that offset with the DECLARE_VVAR macro. (If
* you mess up, the linker will catch it.)
*/
/* Offset of vars within vsyscall page */
#define VSYSCALL_VARS_OFFSET (3072 + 128)
/* Base address of vvars. This is not ABI. */
#define VVAR_ADDRESS (-10*1024*1024 - 4096)
#if defined(__VVAR_KERNEL_LDS)
@ -26,17 +25,17 @@
* right place.
*/
#define DECLARE_VVAR(offset, type, name) \
EMIT_VVAR(name, VSYSCALL_VARS_OFFSET + offset)
EMIT_VVAR(name, offset)
#else
#define DECLARE_VVAR(offset, type, name) \
static type const * const vvaraddr_ ## name = \
(void *)(VSYSCALL_START + VSYSCALL_VARS_OFFSET + (offset));
(void *)(VVAR_ADDRESS + (offset));
#define DEFINE_VVAR(type, name) \
type __vvar_ ## name \
__attribute__((section(".vsyscall_var_" #name), aligned(16)))
type name \
__attribute__((section(".vvar_" #name), aligned(16)))
#define VVAR(name) (*vvaraddr_ ## name)
@ -49,4 +48,3 @@ DECLARE_VVAR(16, int, vgetcpu_mode)
DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)
#undef DECLARE_VVAR
#undef VSYSCALL_VARS_OFFSET