cxl/mbox: Break poison list loop on an empty payload

A device that returns count == 0 with CXL_POISON_FLAG_MORE set on every
iteration never advances nr_records, so the max_errors guard never
trips and the do/while loops forever while holding poison.mutex. That
hangs the sysfs-triggered scan thread and blocks all subsequent poison
operations on the device. The existing "Protect against an uncleared
_FLAG_MORE" guard was intended to bound a misbehaving device but does
not cover the count == 0 case.

Stop the loop on an empty payload so a malfunctioning or malicious
device cannot wedge the poison scan.

Link: https://sashiko.dev/#/patchset/20260702090849.47501-1-icheng@nvidia.com?part=3
Fixes: ed83f7ca398b ("cxl/mbox: Add GET_POISON_LIST mailbox command")
Assisted-by: Claude:claude-opus-4-8
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20260709155714.1893280-1-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

0 files changed, 0 insertions, 0 deletions