cxl/mbox: Treat unknown device return codes as errors

cxl_mbox_cmd_rc2errno() and cxl_mbox_cmd_rc2str() use the device's 16-bit
return code to index cxl_mbox_cmd_rctable[]. A return code outside the
table's range causes an out-of-bounds read, potentially allowing a failed
command to be reported as successful.

Check the return code against the table size. Report unknown codes as
-ENXIO, the errno used for most device-reported errors, and describe them
as "unknown return code".

Found with a QEMU Type-3 device returning codes 001Fh and 0020h, which are
defined in CXL 4.0 but not yet recognized by Linux [1].

[1] https://lore.kernel.org/linux-cxl/20260929060747.3550005-1-huanggaobin23@semi.ac.cn/

Fixes: 92fcc1abab09 ("cxl/mbox: Improve handling of mbox_cmd hw return codes")
Cc: stable@vger.kernel.org
Signed-off-by: Gaobin Huang <huanggaobin23@semi.ac.cn>
Co-developed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Gaobin Huang <huanggaobin23@semi.ac.cn>
Link: https://patch.msgid.link/1c822ac0361e7aecb318b73f0288ad1c862517ff.1793645996.git.alison.schofield@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

0 files changed, 0 insertions, 0 deletions