kprobes: fix a null pointer bug in register_kretprobe()

Fix a bug in regiseter_kretprobe() which does not check rp->kp.symbol_name ==
NULL before calling kprobe_lookup_name.

For maintainability, this introduces kprobe_addr helper function which
resolves addr field.  It is used by register_kprobe and register_kretprobe.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index e6a61dc..fcfb580 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -498,27 +498,36 @@ static int __kprobes in_kprobes_functions(unsigned long addr)
        return 0;
 }
 
+/*
+ * If we have a symbol_name argument, look it up and add the offset field
+ * to it. This way, we can specify a relative address to a symbol.
+ */
+static kprobe_opcode_t __kprobes *kprobe_addr(struct kprobe *p)
+{
+       kprobe_opcode_t *addr = p->addr;
+       if (p->symbol_name) {
+               if (addr)
+                       return NULL;
+               kprobe_lookup_name(p->symbol_name, addr);
+       }
+
+       if (!addr)
+               return NULL;
+       return (kprobe_opcode_t *)(((char *)addr) + p->offset);
+}
+
 static int __kprobes __register_kprobe(struct kprobe *p,
        unsigned long called_from)
 {
        int ret = 0;
        struct kprobe *old_p;
        struct module *probed_mod;
+       kprobe_opcode_t *addr;
 
-       /*
-        * If we have a symbol_name argument look it up,
-        * and add it to the address.  That way the addr
-        * field can either be global or relative to a symbol.
-        */
-       if (p->symbol_name) {
-               if (p->addr)
-                       return -EINVAL;
-               kprobe_lookup_name(p->symbol_name, p->addr);
-       }
-
-       if (!p->addr)
+       addr = kprobe_addr(p);
+       if (!addr)
                return -EINVAL;
-       p->addr = (kprobe_opcode_t *)(((char *)p->addr)+ p->offset);
+       p->addr = addr;
 
        if (!kernel_text_address((unsigned long) p->addr) ||
            in_kprobes_functions((unsigned long) p->addr))
@@ -721,12 +730,12 @@ int __kprobes register_kretprobe(struct kretprobe *rp)
        int ret = 0;
        struct kretprobe_instance *inst;
        int i;
-       void *addr = rp->kp.addr;
+       void *addr;
 
        if (kretprobe_blacklist_size) {
-               if (addr == NULL)
-                       kprobe_lookup_name(rp->kp.symbol_name, addr);
-               addr += rp->kp.offset;
+               addr = kprobe_addr(&rp->kp);
+               if (!addr)
+                       return -EINVAL;
 
                for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
                        if (kretprobe_blacklist[i].addr == addr)