uprobes: Change unregister/apply to WARN() if uprobe/consumer is gone

Add WARN_ON's into uprobe_unregister() and uprobe_apply() to ensure
that nobody tries to play with the dead uprobe/consumer. This helps
to catch the bugs like the one fixed by the previous patch.

In the longer term we should fix this poorly designed interface.
uprobe_register() should return "struct uprobe *" which should be
passed to apply/unregister. Plus other semantic changes, see the
changelog in commit 41ccba029e94.

Link: http://lkml.kernel.org/p/20140627170140.GA18322@redhat.com
Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c445e39..6f3254e 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -846,7 +846,7 @@ static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *u
 {
        int err;
 
-       if (!consumer_del(uprobe, uc))  /* WARN? */
+       if (WARN_ON(!consumer_del(uprobe, uc)))
                return;
 
        err = register_for_each_vma(uprobe, NULL);
@@ -927,7 +927,7 @@ int uprobe_apply(struct inode *inode, loff_t offset,
        int ret = -ENOENT;
 
        uprobe = find_uprobe(inode, offset);
-       if (!uprobe)
+       if (WARN_ON(!uprobe))
                return ret;
 
        down_write(&uprobe->register_rwsem);
@@ -952,7 +952,7 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume
        struct uprobe *uprobe;
 
        uprobe = find_uprobe(inode, offset);
-       if (!uprobe)
+       if (WARN_ON(!uprobe))
                return;
 
        down_write(&uprobe->register_rwsem);