lockdep: fix kernel crash on module unload

Michael Wu noticed in his lkml post at

    http://marc.info/?l=linux-kernel&m=119396182726091&w=2

that certain wireless drivers ended up having their name in module
memory, which would then crash the kernel on module unload.

The patch he proposed was a bit clumsy in that it increased the size of
a lockdep entry significantly; the patch below tries another approach,
it checks, on module teardown, if the name of a class is in module space
and then zaps the class.  This is very similar to what we already do
with keys that are in module space.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 4335f12a27c6..e2c07ece367d 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2932,7 +2932,7 @@ static void zap_class(struct lock_class *class)
 
 }
 
-static inline int within(void *addr, void *start, unsigned long size)
+static inline int within(const void *addr, void *start, unsigned long size)
 {
         return addr >= start && addr < start + size;
 }
@@ -2955,9 +2955,12 @@ void lockdep_free_key_range(void *start, unsigned long size)
                 head = classhash_table + i;
                 if (list_empty(head))
                         continue;
-                list_for_each_entry_safe(class, next, head, hash_entry)
+                list_for_each_entry_safe(class, next, head, hash_entry) {
                         if (within(class->key, start, size))
                                 zap_class(class);
+                        else if (within(class->name, start, size))
+                                zap_class(class);
+                }
         }
 
         if (locked)