Most uring_cmds issued against ublk character devices are serialized
because each command affects only one queue, and there is an early check
which only allows a single task (the queue's ubq_daemon) to issue
uring_cmds against that queue. However, this mechanism does not work for
FETCH_REQs, since they are expected before ubq_daemon is set. Since
FETCH_REQs are only used at initialization and not in the fast path,
serialize them using the per-ublk-device mutex. This fixes a number of
data races that were previously possible if a badly behaved ublk server
decided to issue multiple FETCH_REQs against the same qid/tag
concurrently.
Reported-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
Signed-off-by: Uday Shankar <ushankar@xxxxxxxxxxxxxxx>
---
drivers/block/ublk_drv.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 2fd05c1bd30b03343cb6f357f8c08dd92ff47af9..5535073ccd23dfbbd25830c1722c360146b95662 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1809,8 +1809,8 @@ static void ublk_nosrv_work(struct work_struct *work)
/* device can only be started after all IOs are ready */
static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq)
+ __must_hold(&ub->mutex)
{
- mutex_lock(&ub->mutex);
ubq->nr_io_ready++;
if (ublk_queue_ready(ubq)) {
ubq->ubq_daemon = current;
@@ -1822,7 +1822,6 @@ static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq)
}
if (ub->nr_queues_ready == ub->dev_info.nr_hw_queues)
complete_all(&ub->completion);
- mutex_unlock(&ub->mutex);
}
static void ublk_handle_need_get_data(struct ublk_device *ub, int q_id,
@@ -1962,17 +1961,18 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
case UBLK_IO_UNREGISTER_IO_BUF:
return ublk_unregister_io_buf(cmd, ub_cmd->addr, issue_flags);
case UBLK_IO_FETCH_REQ:
+ mutex_lock(&ub->mutex);
/* UBLK_IO_FETCH_REQ is only allowed before queue is setup */
if (ublk_queue_ready(ubq)) {
ret = -EBUSY;
- goto out;
+ goto out_unlock;
}
/*
* The io is being handled by server, so COMMIT_RQ is expected
* instead of FETCH_REQ
*/
if (io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)
- goto out;
+ goto out_unlock;
if (ublk_need_map_io(ubq)) {
/*
@@ -1980,15 +1980,16 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
* DATA is not enabled
*/
if (!ub_cmd->addr && !ublk_need_get_data(ubq))
- goto out;
+ goto out_unlock;
} else if (ub_cmd->addr) {
/* User copy requires addr to be unset */
ret = -EINVAL;
- goto out;
+ goto out_unlock;
}
ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
ublk_mark_io_ready(ub, ubq);
+ mutex_unlock(&ub->mutex);
break;
case UBLK_IO_COMMIT_AND_FETCH_REQ:
req = blk_mq_tag_to_rq(ub->tag_set.tags[ub_cmd->q_id], tag);
@@ -2028,7 +2029,9 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
ublk_prep_cancel(cmd, issue_flags, ubq, tag);
return -EIOCBQUEUED;
- out:
+out_unlock:
+ mutex_unlock(&ub->mutex);
+out:
pr_devel("%s: complete: cmd op %d, tag %d ret %x io_flags %x\n",
__func__, cmd_op, tag, ret, io->flags);
return ret;
--
2.34.1
