kprobes: Verify jprobe entry point

Verify jprobe's entry point is a function entry point
using kallsyms' offset value.
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
LKML-Reference: <1284512670-2369-3-git-send-email-namhyung@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/kprobes.c

@@ -1339,14 +1339,18 @@ int __kprobes register_jprobes(struct jprobe **jps, int num)
 	if (num <= 0)
 		return -EINVAL;
 	for (i = 0; i < num; i++) {
-		unsigned long addr;
+		unsigned long addr, offset;
 		jp = jps[i];
 		addr = arch_deref_entry_point(jp->entry);
 
-		/* Todo: Verify probepoint is a function entry point */
+		/* Verify probepoint is a function entry point */
+		if (kallsyms_lookup_size_offset(addr, NULL, &offset) &&
+		    offset == 0) {
 			jp->kp.pre_handler = setjmp_pre_handler;
 			jp->kp.break_handler = longjmp_break_handler;
 			ret = register_kprobe(&jp->kp);
+		} else
+			ret = -EINVAL;
 
 		if (ret < 0) {
 			if (i > 0)