riscv: hwprobe: initialize pair->value in hwprobe_one_pair()

The vendor-extension handlers reached from hwprobe_one_pair()
(hwprobe_isa_vendor_ext_thead_0() and friends) only OR the present bits
into pair->value via VENDOR_EXTENSION_SUPPORTED() and clear their own
missing bits; they assume the caller has already zeroed pair->value.

That holds for hwprobe_get_values() (it zeroes each pair) and
hwprobe_get_cpus() (it re-initializes its scratch pair per key), but not
for complete_hwprobe_vdso_data(), which reuses a single pair across all
keys without re-zeroing. A vendor key therefore inherits stale bits from
the previously probed key, and the wrong value is cached in the vDSO
all_cpu_hwprobe_values[] and handed to userspace on the fast patih.

Zero pair->value once at the top of hwprobe_one_pair() so every handler
starts from a clean value regardless of the caller, and drop the now
redundant zeroing in the *_BLOCK_SIZE cases. hwprobe_isa_ext0() keeps its
own zeroing because hwprobe_ext0_has() calls it directly, bypassing
hwprobe_one_pair().

Fixes: a5ea53da65c5 ("riscv: hwprobe: Add thead vendor extension probing")
Signed-off-by: Andy Chiu <tchiu@tenstorrent.com>
Reviewed-by: Jesse Taube <jtaubepe@redhat.com>
Link: https://patch.msgid.link/20260725001614.2578617-2-tchiu@tenstorrent.com
Cc: stable@vger.kernel.org
Signed-off-by: Paul Walmsley <pjw@kernel.org>

0 files changed, 0 insertions, 0 deletions