]> git.openfabrics.org - ~shefty/rdma-dev.git/commitdiff
writeback: fix dereferencing NULL bdi->dev on trace_writeback_queue
authorWu Fengguang <fengguang.wu@intel.com>
Sun, 5 Feb 2012 02:54:03 +0000 (20:54 -0600)
committerWu Fengguang <fengguang.wu@intel.com>
Mon, 6 Feb 2012 03:17:25 +0000 (11:17 +0800)
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>
include/trace/events/writeback.h

index 06d302ebcb726f16d4c36c667a6008512b7247be..5973410e8f8cf34fd9fb1abaedb7325435716f9a 100644 (file)
@@ -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;