[PATCH v2 0/2] ublk: fix auto buf reg ordering around uring_cmd

Two UBLK_F_AUTO_BUF_REG ordering fixes.

Patch 1: invalid auto_buf in sqe->addr can fail after ublk_fill_io_cmd()
has already set UBLK_IO_FLAG_ACTIVE. Split validate/apply so the check
has no side effects, then take the uring_cmd and store the validated
buffer.

Patch 2: batch commit wrote the new auto_buf into io->buf before
ublk_clear_auto_buf_reg(), so unregister could target the new index and
leave the old registered buffer behind. Clear first, then update
io->buf.

Changes in v2:
- patch 1: validate before __ublk_fetch()/fill; apply is infallible
  (per Caleb's review)
- add patch 2 for the batch commit clear/store order

Tested: 
ublk selftests generic_08/09, batch_01..03, stress_08;
liburing uring_cmd_ublk.t

v1: https://lore.kernel.org/linux-block/[email protected]/

Yang Xiuwei (2):
  ublk: validate auto buf reg before taking uring_cmd
  ublk: clear auto buf reg before updating io->buf in batch commit

 drivers/block/ublk_drv.c | 76 +++++++++++++++++++++-------------------
 1 file changed, 39 insertions(+), 37 deletions(-)

-- 
2.25.1