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authorAndy Lutomirski <luto@MIT.EDU>2011-06-05 13:50:19 -0400
committerIngo Molnar <mingo@elte.hu>2011-06-05 21:30:32 +0200
commit9fd67b4ed0714ab718f1f9bd14c344af336a6df7 (patch)
tree7dae7e978b68479b6ee316d92b81d703cee3a894 /arch/x86/include/asm/vvar.h
parent8b4777a4b50cb0c84c1152eac85d24415fb6ff7d (diff)
x86-64: Give vvars their own page
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>
Diffstat (limited to 'arch/x86/include/asm/vvar.h')
-rw-r--r--arch/x86/include/asm/vvar.h22
1 files changed, 10 insertions, 12 deletions
diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h
index a4eaca4a6133..de656ac2af41 100644
--- a/arch/x86/include/asm/vvar.h
+++ b/arch/x86/include/asm/vvar.h
@@ -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