[PATCH 0/2] drbd: validate payload sizes received from the peer

[Yibo Liu <yiboliume@gmail.com>]

Two places in the DRBD receive path take a payload size from the peer's
packet header and use it without comparing it to the size they expect.
Commit bd910a7660d2 ("drbd: reject data replies with an out-of-range
payload size") already rejects negative sizes in recv_dless_read();
these patches cover the remaining cases:

1/2 rejects a P_DATA_REPLY whose size differs from the read request.
    A short reply currently completes the read successfully with part
    of the bio never written.

2/2 rejects P_CSUM_RS_REQUEST and P_OV_REPLY packets whose digest
    length does not match the configured algorithm, and makes the
    worker compare digests only when their sizes match. A short digest
    currently causes an out-of-bounds read in memcmp(), and a huge one
    triggers a page allocator warning.

Like the earlier fixes, this only matters for a peer that does not
follow the protocol; a correct peer always sends the expected sizes.

The problems were found with the help of an AI coding assistant and
were reproduced on block-7.3 before posting (details below the "---" of
each patch). Testing:
- before/after runs of the reproducer in an arm64 virtme-ng KASAN guest
- a complete csums-alg resync and an online verify as regression tests
- each patch built with W=1 and sparse (C=2), arm64, gcc 13.3: no new
  warnings
- checkpatch.pl --strict clean
Not built with clang or for other architectures.

Yibo Liu (2):
  drbd: reject data replies whose size does not match the request
  drbd: validate digest size in checksum resync and verify requests

 drivers/block/drbd/drbd_receiver.c | 14 ++++++++++++--
 drivers/block/drbd/drbd_worker.c   |  8 ++++----
 2 files changed, 16 insertions(+), 6 deletions(-)


base-commit: 41cab3a71dc7be62114d91cc849424879062d324
-- 
2.39.5 (Apple Git-154)