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-rw-r--r--arch/x86/kernel/traps.c77
1 files changed, 47 insertions, 30 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 989514c94a55..446c9ef8cfc3 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -51,6 +51,7 @@
#include <asm/traps.h>
#include <asm/desc.h>
#include <asm/fpu/internal.h>
+#include <asm/cpu_entry_area.h>
#include <asm/mce.h>
#include <asm/fixmap.h>
#include <asm/mach_traps.h>
@@ -348,23 +349,42 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
/*
* If IRET takes a non-IST fault on the espfix64 stack, then we
- * end up promoting it to a doublefault. In that case, modify
- * the stack to make it look like we just entered the #GP
- * handler from user space, similar to bad_iret.
+ * end up promoting it to a doublefault. In that case, take
+ * advantage of the fact that we're not using the normal (TSS.sp0)
+ * stack right now. We can write a fake #GP(0) frame at TSS.sp0
+ * and then modify our own IRET frame so that, when we return,
+ * we land directly at the #GP(0) vector with the stack already
+ * set up according to its expectations.
+ *
+ * The net result is that our #GP handler will think that we
+ * entered from usermode with the bad user context.
*
* No need for ist_enter here because we don't use RCU.
*/
- if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY &&
+ if (((long)regs->sp >> P4D_SHIFT) == ESPFIX_PGD_ENTRY &&
regs->cs == __KERNEL_CS &&
regs->ip == (unsigned long)native_irq_return_iret)
{
- struct pt_regs *normal_regs = task_pt_regs(current);
+ struct pt_regs *gpregs = (struct pt_regs *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
- /* Fake a #GP(0) from userspace. */
- memmove(&normal_regs->ip, (void *)regs->sp, 5*8);
- normal_regs->orig_ax = 0; /* Missing (lost) #GP error code */
+ /*
+ * regs->sp points to the failing IRET frame on the
+ * ESPFIX64 stack. Copy it to the entry stack. This fills
+ * in gpregs->ss through gpregs->ip.
+ *
+ */
+ memmove(&gpregs->ip, (void *)regs->sp, 5*8);
+ gpregs->orig_ax = 0; /* Missing (lost) #GP error code */
+
+ /*
+ * Adjust our frame so that we return straight to the #GP
+ * vector with the expected RSP value. This is safe because
+ * we won't enable interupts or schedule before we invoke
+ * general_protection, so nothing will clobber the stack
+ * frame we just set up.
+ */
regs->ip = (unsigned long)general_protection;
- regs->sp = (unsigned long)&normal_regs->orig_ax;
+ regs->sp = (unsigned long)&gpregs->orig_ax;
return;
}
@@ -389,7 +409,7 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
*
* Processors update CR2 whenever a page fault is detected. If a
* second page fault occurs while an earlier page fault is being
- * deliv- ered, the faulting linear address of the second fault will
+ * delivered, the faulting linear address of the second fault will
* overwrite the contents of CR2 (replacing the previous
* address). These updates to CR2 occur even if the page fault
* results in a double fault or occurs during the delivery of a
@@ -605,14 +625,15 @@ NOKPROBE_SYMBOL(do_int3);
#ifdef CONFIG_X86_64
/*
- * Help handler running on IST stack to switch off the IST stack if the
- * interrupted code was in user mode. The actual stack switch is done in
- * entry_64.S
+ * Help handler running on a per-cpu (IST or entry trampoline) stack
+ * to switch to the normal thread stack if the interrupted code was in
+ * user mode. The actual stack switch is done in entry_64.S
*/
asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs)
{
- struct pt_regs *regs = task_pt_regs(current);
- *regs = *eregs;
+ struct pt_regs *regs = (struct pt_regs *)this_cpu_read(cpu_current_top_of_stack) - 1;
+ if (regs != eregs)
+ *regs = *eregs;
return regs;
}
NOKPROBE_SYMBOL(sync_regs);
@@ -628,13 +649,13 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
/*
* This is called from entry_64.S early in handling a fault
* caused by a bad iret to user mode. To handle the fault
- * correctly, we want move our stack frame to task_pt_regs
- * and we want to pretend that the exception came from the
- * iret target.
+ * correctly, we want to move our stack frame to where it would
+ * be had we entered directly on the entry stack (rather than
+ * just below the IRET frame) and we want to pretend that the
+ * exception came from the IRET target.
*/
struct bad_iret_stack *new_stack =
- container_of(task_pt_regs(current),
- struct bad_iret_stack, regs);
+ (struct bad_iret_stack *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
/* Copy the IRET target to the new stack. */
memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
@@ -795,14 +816,6 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
debug_stack_usage_dec();
exit:
-#if defined(CONFIG_X86_32)
- /*
- * This is the most likely code path that involves non-trivial use
- * of the SYSENTER stack. Check that we haven't overrun it.
- */
- WARN(this_cpu_read(cpu_tss.SYSENTER_stack_canary) != STACK_END_MAGIC,
- "Overran or corrupted SYSENTER stack\n");
-#endif
ist_exit(regs);
}
NOKPROBE_SYMBOL(do_debug);
@@ -929,6 +942,9 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
void __init trap_init(void)
{
+ /* Init cpu_entry_area before IST entries are set up */
+ setup_cpu_entry_areas();
+
idt_setup_traps();
/*
@@ -936,8 +952,9 @@ void __init trap_init(void)
* "sidt" instruction will not leak the location of the kernel, and
* to defend the IDT against arbitrary memory write vulnerabilities.
* It will be reloaded in cpu_init() */
- __set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);
- idt_descr.address = fix_to_virt(FIX_RO_IDT);
+ cea_set_pte(CPU_ENTRY_AREA_RO_IDT_VADDR, __pa_symbol(idt_table),
+ PAGE_KERNEL_RO);
+ idt_descr.address = CPU_ENTRY_AREA_RO_IDT;
/*
* Should be a barrier for any external CPU state: