[PATCH v2 0/2] nvmet: passthru cleanup and fixup I/O hotpath

[Nilay Shroff]

Hi,

This series addresses a race in the passthru I/O hotpath where
concurrently disabling the passthru controller while I/Os are in flight
can result in a use-after-free bug.

We were able to reproduce this bug with NVMe/TCP configured and by
injecting an additional delay into the target-side I/O processing code.
If the passthru controller is disabled while an I/O is still in flight,
it results in the following kernel crash:

BUG: Kernel NULL pointer dereference on read at 0x00000030
[...]
CPU: 9 UID: 0 PID: 4143 Comm: kworker/9:5H Kdump: loaded Not tainted 7.3.0-rc3+ #14 PREEMPT 
Hardware name: IBM,9080-HEX Power11 (architected) 0x820200 0xf000007 of:IBM,FW1110.00 (NH1110_031) hv:phyp pSeries
Workqueue: nvmet_tcp_wq nvmet_tcp_io_work [nvmet_tcp]
[...]
NIP [c0080000156d8fe0] nvmet_passthru_execute_cmd+0x58/0x45c [nvmet]
LR [c0080000156d8fc4] nvmet_passthru_execute_cmd+0x3c/0x45c [nvmet]
Call Trace:
 nvmet_passthru_execute_cmd+0x3c/0x45c [nvmet] (unreliable)
 nvmet_tcp_done_recv_pdu+0x2d0/0x718 [nvmet_tcp]
 nvmet_tcp_try_recv_pdu+0x29c/0x348 [nvmet_tcp]
 nvmet_tcp_io_work+0xe8/0x838 [nvmet_tcp]
 process_one_work+0x224/0x5ec
 worker_thread+0x1f8/0x3e8
 kthread+0x178/0x1ac
 start_kernel_thread+0x14/0x18

There are two patches in this series. The first patch groups all
passthru-related fields into a separate struct nvmet_passthru, which
makes the code easier to maintain and reason about. The second patch
fixes the use-after-free bug described above.

As usual, code review comments and feedback are most welcome!

Thanks!

Changes from v1:
  - In patch 1/2, dynamically allocate struct nvmet_passthru when the
    passthru controller is configured, reducing memory overhead for
    subsystems that don't use passthru. (hch)

Nilay Shroff (2):
  nvmet: introduce struct nvmet_passthru
  nvmet: fix use-after-free in passthru I/O hotpath

 drivers/nvme/target/configfs.c |  90 ++++++++++++++++++++++++----
 drivers/nvme/target/core.c     |  15 ++++-
 drivers/nvme/target/nvmet.h    |  66 +++++++++++++++++++--
 drivers/nvme/target/passthru.c | 103 ++++++++++++++++++++++++++-------
 4 files changed, 232 insertions(+), 42 deletions(-)

-- 
2.53.0