kprobes: initialize before using a hlist
Ananth N Mavinakayanahalli [Fri, 20 Jan 2012 22:34:04 +0000 (14:34 -0800)]
Commit ef53d9c5e ("kprobes: improve kretprobe scalability with hashed
locking") introduced a bug where we can potentially leak
kretprobe_instances since we initialize a hlist head after having used
it.

Initialize the hlist head before using it.

Reported by: Jim Keniston <jkenisto@us.ibm.com>
Acked-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Srinivasa D S <srinivasa@in.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kprobes.c

index 95dd721..29f5b65 100644 (file)
@@ -1077,6 +1077,7 @@ void __kprobes kprobe_flush_task(struct task_struct *tk)
                /* Early boot.  kretprobe_table_locks not yet initialized. */
                return;
 
+       INIT_HLIST_HEAD(&empty_rp);
        hash = hash_ptr(tk, KPROBE_HASH_BITS);
        head = &kretprobe_inst_table[hash];
        kretprobe_table_lock(hash, &flags);
@@ -1085,7 +1086,6 @@ void __kprobes kprobe_flush_task(struct task_struct *tk)
                        recycle_rp_inst(ri, &empty_rp);
        }
        kretprobe_table_unlock(hash, &flags);
-       INIT_HLIST_HEAD(&empty_rp);
        hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
                hlist_del(&ri->hlist);
                kfree(ri);