The access beyond the end of device BUG_ON that was introduced to
dm_request_fn via commit 29e4013de7ad950280e4b2208 ("dm: implement
REQ_FLUSH/FUA support for request-based dm") is an overly drastic
response. Use dm_kill_unmapped_request() to fail the original and
clone request with -EIO.

map_request() will assign the valid target returned by
dm_table_find_target() to tio->ti. But in the case where the target
isn't valid tio->ti is never assigned (because map_request isn't
called); so add a check for tio->ti != NULL to dm_done().

Reported-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v2.6.37+
---
drivers/md/dm.c | 22 +++++++++++++++++-----
1 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4e09b6f..27fb739 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -865,7 +865,10 @@ static void dm_done(struct request *clone, int error, bool mapped)
{
int r = error;
struct dm_rq_target_io *tio = clone->end_io_data;
- dm_request_endio_fn rq_end_io = tio->ti->type->rq_end_io;
+ dm_request_endio_fn rq_end_io = NULL;
+
+ if (tio->ti)
+ rq_end_io = tio->ti->type->rq_end_io;

if (mapped && rq_end_io)
r = rq_end_io(tio->ti, clone, error, &tio->info);
@@ -1651,19 +1654,30 @@ static void dm_request_fn(struct request_queue *q)
if (!rq)
goto delay_and_out;

+ clone = rq->special;
+
/* always use block 0 to find the target for flushes for now */
pos = 0;
if (!(rq->cmd_flags & REQ_FLUSH))
pos = blk_rq_pos(rq);

ti = dm_table_find_target(map, pos);
- BUG_ON(!dm_target_is_valid(ti));
+ if (!dm_target_is_valid(ti)) {
+ /*
+ * Must perform setup, that dm_done() requires,
+ * before calling dm_kill_unmapped_request
+ */
+ blk_start_request(rq);
+ atomic_inc(&md->pending[rq_data_dir(clone)]);
+ dm_get(md);
+ dm_kill_unmapped_request(clone, -EIO);
+ goto out;
+ }

if (ti->type->busy && ti->type->busy(ti))
goto delay_and_out;

blk_start_request(rq);
- clone = rq->special;
atomic_inc(&md->pending[rq_data_dir(clone)]);

spin_unlock(q->queue_lock);
@@ -1684,8 +1698,6 @@ delay_and_out:
blk_delay_queue(q, HZ / 10);
out:
dm_table_put(map);
-
- return;
}

int dm_underlying_device_busy(struct request_queue *q)

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