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>

1 files changed, 26 insertions, 17 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index e6a61dcbc578..fcfb580c3afc 100644
--- 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)