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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
parent8b4777a4b50cb0c84c1152eac85d24415fb6ff7d (diff)
downloadtalos-op-linux-9fd67b4ed0714ab718f1f9bd14c344af336a6df7.tar.gz
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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')
-rw-r--r--arch/x86/include/asm/fixmap.h1
-rw-r--r--arch/x86/include/asm/pgtable_types.h2
-rw-r--r--arch/x86/include/asm/vvar.h22
-rw-r--r--arch/x86/kernel/vmlinux.lds.S28
-rw-r--r--arch/x86/kernel/vsyscall_64.c5
5 files changed, 35 insertions, 23 deletions
diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index 4729b2b63117..460c74e4852c 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -78,6 +78,7 @@ enum fixed_addresses {
VSYSCALL_LAST_PAGE,
VSYSCALL_FIRST_PAGE = VSYSCALL_LAST_PAGE
+ ((VSYSCALL_END-VSYSCALL_START) >> PAGE_SHIFT) - 1,
+ VVAR_PAGE,
VSYSCALL_HPET,
#endif
FIX_DBGP_BASE,
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index d56187c6b838..6a29aed65902 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -108,6 +108,7 @@
#define __PAGE_KERNEL_UC_MINUS (__PAGE_KERNEL | _PAGE_PCD)
#define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RX | _PAGE_USER)
#define __PAGE_KERNEL_VSYSCALL_NOCACHE (__PAGE_KERNEL_VSYSCALL | _PAGE_PCD | _PAGE_PWT)
+#define __PAGE_KERNEL_VVAR (__PAGE_KERNEL_RO | _PAGE_USER)
#define __PAGE_KERNEL_LARGE (__PAGE_KERNEL | _PAGE_PSE)
#define __PAGE_KERNEL_LARGE_NOCACHE (__PAGE_KERNEL | _PAGE_CACHE_UC | _PAGE_PSE)
#define __PAGE_KERNEL_LARGE_EXEC (__PAGE_KERNEL_EXEC | _PAGE_PSE)
@@ -130,6 +131,7 @@
#define PAGE_KERNEL_LARGE_EXEC __pgprot(__PAGE_KERNEL_LARGE_EXEC)
#define PAGE_KERNEL_VSYSCALL __pgprot(__PAGE_KERNEL_VSYSCALL)
#define PAGE_KERNEL_VSYSCALL_NOCACHE __pgprot(__PAGE_KERNEL_VSYSCALL_NOCACHE)
+#define PAGE_KERNEL_VVAR __pgprot(__PAGE_KERNEL_VVAR)
#define PAGE_KERNEL_IO __pgprot(__PAGE_KERNEL_IO)
#define PAGE_KERNEL_IO_NOCACHE __pgprot(__PAGE_KERNEL_IO_NOCACHE)
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
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 89aed99aafce..98b378dc7f86 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -161,12 +161,6 @@ SECTIONS
#define VVIRT_OFFSET (VSYSCALL_ADDR - __vsyscall_0)
#define VVIRT(x) (ADDR(x) - VVIRT_OFFSET)
-#define EMIT_VVAR(x, offset) .vsyscall_var_ ## x \
- ADDR(.vsyscall_0) + offset \
- : AT(VLOAD(.vsyscall_var_ ## x)) { \
- *(.vsyscall_var_ ## x) \
- } \
- x = VVIRT(.vsyscall_var_ ## x);
. = ALIGN(4096);
__vsyscall_0 = .;
@@ -192,19 +186,31 @@ SECTIONS
*(.vsyscall_3)
}
-#define __VVAR_KERNEL_LDS
-#include <asm/vvar.h>
-#undef __VVAR_KERNEL_LDS
-
- . = __vsyscall_0 + PAGE_SIZE;
+ . = ALIGN(__vsyscall_0 + PAGE_SIZE, PAGE_SIZE);
#undef VSYSCALL_ADDR
#undef VLOAD_OFFSET
#undef VLOAD
#undef VVIRT_OFFSET
#undef VVIRT
+
+ __vvar_page = .;
+
+ .vvar : AT(ADDR(.vvar) - LOAD_OFFSET) {
+
+ /* Place all vvars at the offsets in asm/vvar.h. */
+#define EMIT_VVAR(name, offset) \
+ . = offset; \
+ *(.vvar_ ## name)
+#define __VVAR_KERNEL_LDS
+#include <asm/vvar.h>
+#undef __VVAR_KERNEL_LDS
#undef EMIT_VVAR
+ } :data
+
+ . = ALIGN(__vvar_page + PAGE_SIZE, PAGE_SIZE);
+
#endif /* CONFIG_X86_64 */
/* Init code and data - will be freed after init */
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 3e682184d76c..3cf1cef75a6a 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -284,9 +284,14 @@ void __init map_vsyscall(void)
{
extern char __vsyscall_0;
unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);
+ extern char __vvar_page;
+ unsigned long physaddr_vvar_page = __pa_symbol(&__vvar_page);
/* Note that VSYSCALL_MAPPED_PAGES must agree with the code below. */
__set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_page0, PAGE_KERNEL_VSYSCALL);
+ __set_fixmap(VVAR_PAGE, physaddr_vvar_page, PAGE_KERNEL_VVAR);
+ BUILD_BUG_ON((unsigned long)__fix_to_virt(VVAR_PAGE) !=
+ (unsigned long)VVAR_ADDRESS);
}
static int __init vsyscall_init(void)
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