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authorWu Fengguang <fengguang.wu@intel.com>2012-02-04 20:54:03 -0600
committerWu Fengguang <fengguang.wu@intel.com>2012-02-06 11:17:25 +0800
commit977b7e3a52a7421ad33a393a38ece59f3d41c2fa (patch)
tree8ad7bb97c2385c3407c4fb647cc932978057559d /include/trace
parent3310225dfc71a35a2cc9340c15c0e08b14b3c754 (diff)
downloadlinux-linaro-stable-977b7e3a52a7421ad33a393a38ece59f3d41c2fa.tar.gz
writeback: fix dereferencing NULL bdi->dev on trace_writeback_queue
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 Cc: stable@kernel.org Reported-by: Rabin Vincent <rabin@rab.in> Tested-by: Namjae Jeon <linkinjeon@gmail.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Diffstat (limited to 'include/trace')
-rw-r--r--include/trace/events/writeback.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 06d302ebcb72..5973410e8f8c 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;