Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty...

Pull module preemption fix from Rusty Russell:
 "Turns out we should have always been disabling preemption here;
  someone finally caught it thanks to Peter Z's additional checks"

* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux:
  module: Fix locking in symbol_put_addr()

diff --git a/kernel/module.c b/kernel/module.c
index b86b7bf1be388d72fe92fb6038b4a67b4710df1f..8f051a106676fb8f2d5457a9104340cce81ce37a 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1063,11 +1063,15 @@ void symbol_put_addr(void *addr)
        if (core_kernel_text(a))
                return;
 
-       /* module_text_address is safe here: we're supposed to have reference
-        * to module from symbol_get, so it can't go away. */
+       /*
+        * Even though we hold a reference on the module; we still need to
+        * disable preemption in order to safely traverse the data structure.
+        */
+       preempt_disable();
        modaddr = __module_text_address(a);
        BUG_ON(!modaddr);
        module_put(modaddr);
+       preempt_enable();
 }
 EXPORT_SYMBOL_GPL(symbol_put_addr);