diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2010-03-06 02:32:29 +0000 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2010-03-06 02:32:29 +0000 |
| commit | a97f925a32aad2a37971d7bfb657006acf04e42d (patch) | |
| tree | 38c74c60f756dd05611138f864340a31f4fc393f | |
| parent | 8215d6ec5fee1e76545decea2cd73717efb5cb42 (diff) | |
dm: free dm_io before bio_endio not after
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>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
| -rw-r--r-- | drivers/md/dm.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 21222f5193f..7199846364e 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); } } |