Messages in this thread Patch in this message | | | Date | Fri, 12 Mar 2010 16:13:31 -0800 | From | Greg KH <> | Subject | [patch 113/123] dm: free dm_io before bio_endio not after |
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2.6.33-stable review patch. If anyone has any objections, please let me know.
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From: Mikulas Patocka <mpatocka@redhat.com>
commit a97f925a32aad2a37971d7bfb657006acf04e42d upstream.
Free the dm_io structure before calling bio_endio() instead of after it, to ensure that the io_pool containing it is not referenced after it is freed.
This partially fixes a problem described here https://www.redhat.com/archives/dm-devel/2010-February/msg00109.html
thread 1: bio_endio(bio, io_error); /* scheduling happens */ thread 2: close the device remove the device thread 1: free_io(md, io);
Thread 2, when removing the device, sees non-empty md->io_pool (because the io hasn't been freed by thread 1 yet) and may crash with BUG in mempool_free. Thread 1 may also crash, when freeing into a nonexisting mempool.
To fix this we must make sure that bio_endio() is the last call and the md structure is not accessed afterwards.
There is another bio_endio in process_barrier, but it is called from the thread and the thread is destroyed prior to freeing the mempools, so this call is not affected by the bug.
A similar bug exists with module unloads - the module may be unloaded immediately after bio_endio - but that is more difficult to fix.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/md/dm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -635,8 +635,10 @@ static void dec_pending(struct dm_io *io if (!md->barrier_error && io_error != -EOPNOTSUPP) md->barrier_error = io_error; end_io_acct(io); + free_io(md, io); } else { end_io_acct(io); + free_io(md, io); if (io_error != DM_ENDIO_REQUEUE) { trace_block_bio_complete(md->queue, bio); @@ -644,8 +646,6 @@ static void dec_pending(struct dm_io *io bio_endio(bio, io_error); } } - - free_io(md, io); } }
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