ChangeSet 1.2231.1.59, 2005/03/28 19:33:04-08:00, [EMAIL PROTECTED]
[PATCH] x86_64: Nop out system call instruction in vsyscall page when
not needed
Nop out system call instruction in vsyscall page when not needed. This
may
make some attacks more difficult.
Signed-off-by: Andi Kleen <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
vsyscall.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 files changed, 69 insertions(+), 5 deletions(-)
diff -Nru a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
--- a/arch/x86_64/kernel/vsyscall.c 2005-03-28 21:19:27 -08:00
+++ b/arch/x86_64/kernel/vsyscall.c 2005-03-28 21:19:27 -08:00
@@ -13,8 +13,8 @@
* vsyscalls. One vsyscall can reserve more than 1 slot to avoid
* jumping out of line if necessary.
*
- * Note: the concept clashes with user mode linux. If you use UML just
- * set the kernel.vsyscall sysctl to 0.
+ * Note: the concept clashes with user mode linux. If you use UML and
+ * want per guest time just set the kernel.vsyscall64 sysctl to 0.
*/
/*
@@ -41,6 +41,7 @@
#include <linux/timer.h>
#include <linux/seqlock.h>
#include <linux/jiffies.h>
+#include <linux/sysctl.h>
#include <asm/vsyscall.h>
#include <asm/pgtable.h>
@@ -107,7 +108,7 @@
static force_inline int gettimeofday(struct timeval *tv, struct timezone *tz)
{
int ret;
- asm volatile("syscall"
+ asm volatile("vsysc2: syscall"
: "=a" (ret)
: "0" (__NR_gettimeofday),"D" (tv),"S" (tz) : __syscall_clobber
);
return ret;
@@ -116,7 +117,7 @@
static force_inline long time_syscall(long *t)
{
long secs;
- asm volatile("syscall"
+ asm volatile("vsysc1: syscall"
: "=a" (secs)
: "0" (__NR_time),"D" (t) : __syscall_clobber);
return secs;
@@ -154,6 +155,69 @@
return -ENOSYS;
}
+#ifdef CONFIG_SYSCTL
+
+#define SYSCALL 0x050f
+#define NOP2 0x9090
+
+/*
+ * NOP out syscall in vsyscall page when not needed.
+ */
+static int vsyscall_sysctl_change(ctl_table *ctl, int write, struct file *
filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ extern u16 vsysc1, vsysc2;
+ u16 *map1, *map2;
+ int ret = proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
+ if (!write)
+ return ret;
+ /* gcc has some trouble with __va(__pa()), so just do it this
+ way. */
+ map1 = ioremap(__pa_symbol(&vsysc1), 2);
+ if (!map1)
+ return -ENOMEM;
+ map2 = ioremap(__pa_symbol(&vsysc2), 2);
+ if (!map2) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ if (!sysctl_vsyscall) {
+ *map1 = SYSCALL;
+ *map2 = SYSCALL;
+ } else {
+ *map1 = NOP2;
+ *map2 = NOP2;
+ }
+ iounmap(map2);
+out:
+ iounmap(map1);
+ return ret;
+}
+
+static int vsyscall_sysctl_nostrat(ctl_table *t, int __user *name, int nlen,
+ void __user *oldval, size_t __user *oldlenp,
+ void __user *newval, size_t newlen,
+ void **context)
+{
+ return -ENOSYS;
+}
+
+static ctl_table kernel_table2[] = {
+ { .ctl_name = 99, .procname = "vsyscall64",
+ .data = &sysctl_vsyscall, .maxlen = sizeof(int), .mode = 0644,
+ .strategy = vsyscall_sysctl_nostrat,
+ .proc_handler vsyscall_sysctl_change },
+ { 0, }
+};
+
+static ctl_table kernel_root_table2[] = {
+ { .ctl_name = CTL_KERN, .procname = "kernel", .mode = 0555,
+ .child = kernel_table2 },
+ { 0 },
+};
+
+#endif
+
static void __init map_vsyscall(void)
{
extern char __vsyscall_0;
@@ -170,7 +234,7 @@
BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE)));
map_vsyscall();
sysctl_vsyscall = 1;
-
+ register_sysctl_table(kernel_root_table2, 0);
return 0;
}
-
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