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>

1 files changed, 18 insertions, 23 deletions

diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
index a575059fb42..5df19a9f923 100644
--- 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)