From: Mikulas Patocka Date: Sat, 6 Mar 2010 02:32:29 +0000 (+0000) Subject: dm: free dm_io before bio_endio not after X-Git-Tag: v2.6.33.1~11 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f64089821be953b9b5b5ff49172780c929786614;p=karo-tx-linux.git dm: free dm_io before bio_endio not after 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 Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/md/dm.c b/drivers/md/dm.c index aa4e2aa86d49..fa786b9d8ba7 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -635,8 +635,10 @@ static void dec_pending(struct dm_io *io, int error) 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, int error) bio_endio(bio, io_error); } } - - free_io(md, io); } }