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Diffstat (limited to 'arch/x86/kernel/vsyscall_64.c')
-rw-r--r--arch/x86/kernel/vsyscall_64.c274
1 files changed, 174 insertions, 100 deletions
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index dda7dff9cef..ea5b5709aa7 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -18,8 +18,7 @@
* use the vDSO.
*/
-/* Disable profiling for userspace code: */
-#define DISABLE_BRANCH_PROFILING
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/time.h>
#include <linux/init.h>
@@ -28,7 +27,8 @@
#include <linux/seqlock.h>
#include <linux/jiffies.h>
#include <linux/sysctl.h>
-#include <linux/clocksource.h>
+#include <linux/topology.h>
+#include <linux/timekeeper_internal.h>
#include <linux/getcpu.h>
#include <linux/cpu.h>
#include <linux/smp.h>
@@ -47,68 +47,51 @@
#include <asm/segment.h>
#include <asm/desc.h>
#include <asm/topology.h>
-#include <asm/vgtod.h>
#include <asm/traps.h>
-DEFINE_VVAR(int, vgetcpu_mode);
-DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data) =
-{
- .lock = __SEQLOCK_UNLOCKED(__vsyscall_gtod_data.lock),
-};
+#define CREATE_TRACE_POINTS
+#include "vsyscall_trace.h"
-void update_vsyscall_tz(void)
-{
- unsigned long flags;
+DEFINE_VVAR(int, vgetcpu_mode);
- write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
- /* sys_tz has changed */
- vsyscall_gtod_data.sys_tz = sys_tz;
- write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
-}
+static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
-void update_vsyscall(struct timespec *wall_time, struct timespec *wtm,
- struct clocksource *clock, u32 mult)
+static int __init vsyscall_setup(char *str)
{
- unsigned long flags;
-
- write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
-
- /* copy vsyscall data */
- vsyscall_gtod_data.clock.vclock_mode = clock->archdata.vclock_mode;
- vsyscall_gtod_data.clock.cycle_last = clock->cycle_last;
- vsyscall_gtod_data.clock.mask = clock->mask;
- vsyscall_gtod_data.clock.mult = mult;
- vsyscall_gtod_data.clock.shift = clock->shift;
- vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
- vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
- vsyscall_gtod_data.wall_to_monotonic = *wtm;
- vsyscall_gtod_data.wall_time_coarse = __current_kernel_time();
-
- write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
+ if (str) {
+ if (!strcmp("emulate", str))
+ vsyscall_mode = EMULATE;
+ else if (!strcmp("native", str))
+ vsyscall_mode = NATIVE;
+ else if (!strcmp("none", str))
+ vsyscall_mode = NONE;
+ else
+ return -EINVAL;
+
+ return 0;
+ }
+
+ return -EINVAL;
}
+early_param("vsyscall", vsyscall_setup);
static void warn_bad_vsyscall(const char *level, struct pt_regs *regs,
const char *message)
{
- static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
- struct task_struct *tsk;
-
- if (!show_unhandled_signals || !__ratelimit(&rs))
+ if (!show_unhandled_signals)
return;
- tsk = current;
-
- printk("%s%s[%d] %s ip:%lx cs:%lx sp:%lx ax:%lx si:%lx di:%lx\n",
- level, tsk->comm, task_pid_nr(tsk),
- message, regs->ip - 2, regs->cs,
- regs->sp, regs->ax, regs->si, regs->di);
+ pr_notice_ratelimited("%s%s[%d] %s ip:%lx cs:%lx sp:%lx ax:%lx si:%lx di:%lx\n",
+ level, current->comm, task_pid_nr(current),
+ message, regs->ip, regs->cs,
+ regs->sp, regs->ax, regs->si, regs->di);
}
static int addr_to_vsyscall_nr(unsigned long addr)
{
int nr;
- if ((addr & ~0xC00UL) != VSYSCALL_START)
+ if ((addr & ~0xC00UL) != VSYSCALL_ADDR)
return -EINVAL;
nr = (addr & 0xC00UL) >> 10;
@@ -118,53 +101,138 @@ static int addr_to_vsyscall_nr(unsigned long addr)
return nr;
}
-void dotraplinkage do_emulate_vsyscall(struct pt_regs *regs, long error_code)
+static bool write_ok_or_segv(unsigned long ptr, size_t size)
+{
+ /*
+ * XXX: if access_ok, get_user, and put_user handled
+ * sig_on_uaccess_error, this could go away.
+ */
+
+ if (!access_ok(VERIFY_WRITE, (void __user *)ptr, size)) {
+ siginfo_t info;
+ struct thread_struct *thread = &current->thread;
+
+ thread->error_code = 6; /* user fault, no page, write */
+ thread->cr2 = ptr;
+ thread->trap_nr = X86_TRAP_PF;
+
+ memset(&info, 0, sizeof(info));
+ info.si_signo = SIGSEGV;
+ info.si_errno = 0;
+ info.si_code = SEGV_MAPERR;
+ info.si_addr = (void __user *)ptr;
+
+ force_sig_info(SIGSEGV, &info, current);
+ return false;
+ } else {
+ return true;
+ }
+}
+
+bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
{
struct task_struct *tsk;
unsigned long caller;
- int vsyscall_nr;
+ int vsyscall_nr, syscall_nr, tmp;
+ int prev_sig_on_uaccess_error;
long ret;
- local_irq_enable();
-
/*
- * Real 64-bit user mode code has cs == __USER_CS. Anything else
- * is bogus.
+ * No point in checking CS -- the only way to get here is a user mode
+ * trap to a high address, which means that we're in 64-bit user code.
*/
- if (regs->cs != __USER_CS) {
- /*
- * If we trapped from kernel mode, we might as well OOPS now
- * instead of returning to some random address and OOPSing
- * then.
- */
- BUG_ON(!user_mode(regs));
- /* Compat mode and non-compat 32-bit CS should both segfault. */
- warn_bad_vsyscall(KERN_WARNING, regs,
- "illegal int 0xcc from 32-bit mode");
- goto sigsegv;
+ WARN_ON_ONCE(address != regs->ip);
+
+ if (vsyscall_mode == NONE) {
+ warn_bad_vsyscall(KERN_INFO, regs,
+ "vsyscall attempted with vsyscall=none");
+ return false;
}
- /*
- * x86-ism here: regs->ip points to the instruction after the int 0xcc,
- * and int 0xcc is two bytes long.
- */
- vsyscall_nr = addr_to_vsyscall_nr(regs->ip - 2);
+ vsyscall_nr = addr_to_vsyscall_nr(address);
+
+ trace_emulate_vsyscall(vsyscall_nr);
+
if (vsyscall_nr < 0) {
warn_bad_vsyscall(KERN_WARNING, regs,
- "illegal int 0xcc (exploit attempt?)");
+ "misaligned vsyscall (exploit attempt or buggy program) -- look up the vsyscall kernel parameter if you need a workaround");
goto sigsegv;
}
if (get_user(caller, (unsigned long __user *)regs->sp) != 0) {
- warn_bad_vsyscall(KERN_WARNING, regs, "int 0xcc with bad stack (exploit attempt?)");
+ warn_bad_vsyscall(KERN_WARNING, regs,
+ "vsyscall with bad stack (exploit attempt?)");
goto sigsegv;
}
tsk = current;
- if (seccomp_mode(&tsk->seccomp))
- do_exit(SIGKILL);
+ /*
+ * Check for access_ok violations and find the syscall nr.
+ *
+ * NULL is a valid user pointer (in the access_ok sense) on 32-bit and
+ * 64-bit, so we don't need to special-case it here. For all the
+ * vsyscalls, NULL means "don't write anything" not "write it at
+ * address 0".
+ */
+ switch (vsyscall_nr) {
+ case 0:
+ if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) ||
+ !write_ok_or_segv(regs->si, sizeof(struct timezone))) {
+ ret = -EFAULT;
+ goto check_fault;
+ }
+
+ syscall_nr = __NR_gettimeofday;
+ break;
+
+ case 1:
+ if (!write_ok_or_segv(regs->di, sizeof(time_t))) {
+ ret = -EFAULT;
+ goto check_fault;
+ }
+
+ syscall_nr = __NR_time;
+ break;
+
+ case 2:
+ if (!write_ok_or_segv(regs->di, sizeof(unsigned)) ||
+ !write_ok_or_segv(regs->si, sizeof(unsigned))) {
+ ret = -EFAULT;
+ goto check_fault;
+ }
+
+ syscall_nr = __NR_getcpu;
+ break;
+ }
+
+ /*
+ * Handle seccomp. regs->ip must be the original value.
+ * See seccomp_send_sigsys and Documentation/prctl/seccomp_filter.txt.
+ *
+ * We could optimize the seccomp disabled case, but performance
+ * here doesn't matter.
+ */
+ regs->orig_ax = syscall_nr;
+ regs->ax = -ENOSYS;
+ tmp = secure_computing(syscall_nr);
+ if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
+ warn_bad_vsyscall(KERN_DEBUG, regs,
+ "seccomp tried to change syscall nr or ip");
+ do_exit(SIGSYS);
+ }
+ if (tmp)
+ goto do_ret; /* skip requested */
+
+ /*
+ * With a real vsyscall, page faults cause SIGSEGV. We want to
+ * preserve that behavior to make writing exploits harder.
+ */
+ prev_sig_on_uaccess_error = current_thread_info()->sig_on_uaccess_error;
+ current_thread_info()->sig_on_uaccess_error = 1;
+
+ ret = -EFAULT;
switch (vsyscall_nr) {
case 0:
ret = sys_gettimeofday(
@@ -179,43 +247,47 @@ void dotraplinkage do_emulate_vsyscall(struct pt_regs *regs, long error_code)
case 2:
ret = sys_getcpu((unsigned __user *)regs->di,
(unsigned __user *)regs->si,
- 0);
+ NULL);
break;
}
+ current_thread_info()->sig_on_uaccess_error = prev_sig_on_uaccess_error;
+
+check_fault:
if (ret == -EFAULT) {
- /*
- * Bad news -- userspace fed a bad pointer to a vsyscall.
- *
- * With a real vsyscall, that would have caused SIGSEGV.
- * To make writing reliable exploits using the emulated
- * vsyscalls harder, generate SIGSEGV here as well.
- */
+ /* Bad news -- userspace fed a bad pointer to a vsyscall. */
warn_bad_vsyscall(KERN_INFO, regs,
"vsyscall fault (exploit attempt?)");
- goto sigsegv;
+
+ /*
+ * If we failed to generate a signal for any reason,
+ * generate one here. (This should be impossible.)
+ */
+ if (WARN_ON_ONCE(!sigismember(&tsk->pending.signal, SIGBUS) &&
+ !sigismember(&tsk->pending.signal, SIGSEGV)))
+ goto sigsegv;
+
+ return true; /* Don't emulate the ret. */
}
regs->ax = ret;
+do_ret:
/* Emulate a ret instruction. */
regs->ip = caller;
regs->sp += 8;
-
- local_irq_disable();
- return;
+ return true;
sigsegv:
- regs->ip -= 2; /* The faulting instruction should be the int 0xcc. */
force_sig(SIGSEGV, current);
- local_irq_disable();
+ return true;
}
/*
* Assume __initcall executes before all user space. Hopefully kmod
* doesn't violate that. We'll find out if it does.
*/
-static void __cpuinit vsyscall_set_cpu(int cpu)
+static void vsyscall_set_cpu(int cpu)
{
unsigned long d;
unsigned long node = 0;
@@ -237,13 +309,13 @@ static void __cpuinit vsyscall_set_cpu(int cpu)
write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
}
-static void __cpuinit cpu_vsyscall_init(void *arg)
+static void cpu_vsyscall_init(void *arg)
{
/* preemption should be already off */
vsyscall_set_cpu(raw_smp_processor_id());
}
-static int __cpuinit
+static int
cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg)
{
long cpu = (long)arg;
@@ -256,24 +328,26 @@ cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg)
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);
+ extern char __vsyscall_page;
+ unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
+
+ __set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
+ vsyscall_mode == NATIVE
+ ? PAGE_KERNEL_VSYSCALL
+ : PAGE_KERNEL_VVAR);
+ BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=
+ (unsigned long)VSYSCALL_ADDR);
}
static int __init vsyscall_init(void)
{
- BUG_ON(VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE));
+ cpu_notifier_register_begin();
on_each_cpu(cpu_vsyscall_init, NULL, 1);
/* notifier priority > KVM */
- hotcpu_notifier(cpu_vsyscall_notifier, 30);
+ __hotcpu_notifier(cpu_vsyscall_notifier, 30);
+
+ cpu_notifier_register_done();
return 0;
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-12-10 14:52:17 +0000