x86: kprobes bugfix

Kprobes for x86-64 may cause a kernel crash if it inserted on "iret"
instruction. "call absolute" is invalid on x86-64, so we don't need
treat it.

 - Change the processing order as same as x86-32.
 - Add "iret"(0xcf) case.
 - Remove next_rip local variable.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
index a575059..5df19a9 100644 (file)
--- a/arch/x86/kernel/kprobes_64.c
+++ b/arch/x86/kernel/kprobes_64.c
@@ -485,7 +485,6 @@ static void __kprobes resume_execution(struct kprobe *p,
                struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 {
        unsigned long *tos = (unsigned long *)regs->rsp;
-       unsigned long next_rip = 0;
        unsigned long copy_rip = (unsigned long)p->ainsn.insn;
        unsigned long orig_rip = (unsigned long)p->addr;
        kprobe_opcode_t *insn = p->ainsn.insn;
@@ -494,46 +493,42 @@ static void __kprobes resume_execution(struct kprobe *p,
        if (*insn >= 0x40 && *insn <= 0x4f)
                insn++;
 
+       regs->eflags &= ~TF_MASK;
        switch (*insn) {
-       case 0x9c:              /* pushfl */
+       case 0x9c:      /* pushfl */
                *tos &= ~(TF_MASK | IF_MASK);
                *tos |= kcb->kprobe_old_rflags;
                break;
-       case 0xc3:              /* ret/lret */
-       case 0xcb:
-       case 0xc2:
+       case 0xc2:      /* iret/ret/lret */
+       case 0xc3:
        case 0xca:
-               regs->eflags &= ~TF_MASK;
-               /* rip is already adjusted, no more changes required*/
-               return;
-       case 0xe8:              /* call relative - Fix return addr */
+       case 0xcb:
+       case 0xcf:
+       case 0xea:      /* jmp absolute -- ip is correct */
+               /* ip is already adjusted, no more changes required */
+               goto no_change;
+       case 0xe8:      /* call relative - Fix return addr */
                *tos = orig_rip + (*tos - copy_rip);
                break;
        case 0xff:
                if ((insn[1] & 0x30) == 0x10) {
                        /* call absolute, indirect */
-                       /* Fix return addr; rip is correct. */
-                       next_rip = regs->rip;
+                       /* Fix return addr; ip is correct. */
                        *tos = orig_rip + (*tos - copy_rip);
+                       goto no_change;
                } else if (((insn[1] & 0x31) == 0x20) ||        /* jmp near, absolute indirect */
                           ((insn[1] & 0x31) == 0x21)) {        /* jmp far, absolute indirect */
-                       /* rip is correct. */
-                       next_rip = regs->rip;
+                       /* ip is correct. */
+                       goto no_change;
                }
-               break;
-       case 0xea:              /* jmp absolute -- rip is correct */
-               next_rip = regs->rip;
-               break;
        default:
                break;
        }
 
-       regs->eflags &= ~TF_MASK;
-       if (next_rip) {
-               regs->rip = next_rip;
-       } else {
-               regs->rip = orig_rip + (regs->rip - copy_rip);
-       }
+       regs->rip = orig_rip + (regs->rip - copy_rip);
+no_change:
+
+       return;
 }
 
 int __kprobes post_kprobe_handler(struct pt_regs *regs)