diff options
| author | Wu Fengguang <fengguang.wu@intel.com> | 2012-02-04 20:54:03 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-02-20 12:46:17 -0800 |
| commit | 422204b77968331ce85721527f7ece49f72658f2 (patch) | |
| tree | d240880498bd55da47b97fcce0c64637fc1c14dc | |
| parent | aec14f459cc9d40f9fd4a7aad2be761de084b320 (diff) | |
| download | lwn-422204b77968331ce85721527f7ece49f72658f2.tar.gz lwn-422204b77968331ce85721527f7ece49f72658f2.zip | |
writeback: fix dereferencing NULL bdi->dev on trace_writeback_queue
commit 977b7e3a52a7421ad33a393a38ece59f3d41c2fa upstream.
When a SD card is hot removed without umount, del_gendisk() will call
bdi_unregister() without destroying/freeing it. This leaves the bdi in
the bdi->dev = NULL, bdi->wb.task = NULL, bdi->bdi_list removed state.
When sync(2) gets the bdi before bdi_unregister() and calls
bdi_queue_work() after the unregister, trace_writeback_queue will be
dereferencing the NULL bdi->dev. Fix it with a simple test for NULL.
LKML-reference: http://lkml.org/lkml/2012/1/18/346
Reported-by: Rabin Vincent <rabin@rab.in>
Tested-by: Namjae Jeon <linkinjeon@gmail.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | include/trace/events/writeback.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index 46e389cf3063..1f48f148f86a 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -47,7 +47,10 @@ DECLARE_EVENT_CLASS(writeback_work_class, __field(int, reason) ), TP_fast_assign( - strncpy(__entry->name, dev_name(bdi->dev), 32); + struct device *dev = bdi->dev; + if (!dev) + dev = default_backing_dev_info.dev; + strncpy(__entry->name, dev_name(dev), 32); __entry->nr_pages = work->nr_pages; __entry->sb_dev = work->sb ? work->sb->s_dev : 0; __entry->sync_mode = work->sync_mode; |