plugins/wdc: clamp unsupported-count in OCP C5 log and bound printed/JSON strings

[prabhakarpujeri]

Summary

The OCP C5 unsupported-requirements log page is device-supplied. Both
printers used the device-reported unsupported_count (__le16) as the loop bound
against the fixed WDC_NUM_UNSUPPORTED_REQ_ENTRIES (253)-entry
unsupported_req_list table, which lives inside the 4096-byte log page:

for (j = 0; j < le16_to_cpu(log_data->unsupported_count); j++)
    printf("  Unsupported Requirement List %d	: %s
", j,
           log_data->unsupported_req_list[j]);

A device reporting a count above 253 (up to 0xFFFF) walks the
16-byte list entries past the buffer — leaking heap content into
stdout in the plain view and into json_object_add_value_string()
in the JSON view.

This is the same "device-supplied count vs fixed-size on-disk table"
pattern as #3993 (seagate fw-activate-history).

Fix

• Clamp log_data->unsupported_count to
  WDC_NUM_UNSUPPORTED_REQ_ENTRIES in wdc_print_unsupported_reqs_log(),
  right when the log page is dispatched — both views see the bounded value.
• Bound the embedded 16-byte ID string so unterminated device data cannot run
  past a list entry: plain view uses %.16s precision; JSON view now uses
  json_object_new_string_len() (matches ocp/solidigm style in-tree).

Testing

• meson setup build-main && ninja -C build-main: clean.
• Hostile-input harness (ASan+UBSan) driving the walk loop with
  unsupported_count = 0xFFFF:
  • pre-fix: heap-buffer-overflow — read of size 1 at 0 bytes past a
    4096-byte region;
  • post-fix: loop walks exactly 253 entries, exit 0.

[igaw]

looks like when json-c is disabled there is a problem:

FAILED: nvme.p/plugins_wdc_wdc-nvme.c.o 
gcc -Invme.p -I. -I.. -Isrc -I../src -Iccan -I../ccan -Ilibnvme/src -I../libnvme/src -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Werror -std=gnu11 -O3 -fomit-frame-pointer -D_GNU_SOURCE -include /__w/nvme-cli/nvme-cli/.build-ci/nvme-config.h -MD -MQ nvme.p/plugins_wdc_wdc-nvme.c.o -MF nvme.p/plugins_wdc_wdc-nvme.c.o.d -o nvme.p/plugins_wdc_wdc-nvme.c.o -c ../plugins/wdc/wdc-nvme.c
In file included from ../src/nvme-print.h:10,
                 from ../plugins/wdc/wdc-nvme.c:48:
../plugins/wdc/wdc-nvme.c: In function ‘wdc_print_unsupported_reqs_log_json’:
../plugins/wdc/wdc-nvme.c:5422:25: error: implicit declaration of function ‘json_object_new_string_len’; did you mean ‘json_object_add_string’? [-Wimplicit-function-declaration]
 5422 |                         json_object_new_string_len(
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~
../src/nvme-json.h:68:49: note: in definition of macro ‘json_object_object_add’
   68 | #define json_object_object_add(o, k, v) ((void)(v))
      |                                                 ^