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| author | Wu Fengguang <fengguang.wu@intel.com> | 2012-02-04 20:54:03 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-02-20 12:48:11 -0800 |
| commit | a5e2201319ef3c88cf8d777466c0e097625ba942 (patch) | |
| tree | 5a117e1300f8112093370a294a0d04849e6e1f13 | |
| parent | 36935521cd67e3df9a1db71591cf224252d6082c (diff) | |
| download | lwn-a5e2201319ef3c88cf8d777466c0e097625ba942.tar.gz lwn-a5e2201319ef3c88cf8d777466c0e097625ba942.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 4e249b927eaa..9b60c6fc6df7 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -23,7 +23,10 @@ DECLARE_EVENT_CLASS(writeback_work_class, __field(int, for_background) ), 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; |