nvdimm: ndtest: Return the string length from flags_show()

flags_show() build their output with a seq_buf and return seq_buf_used(),
which may include the trailing NUL byte when the seq_buf has
overflowed. Use seq_buf_strlen() instead.

The flag names are far shorter than the PAGE_SIZE buffer sysfs
provides, so this cannot overflow today.

Build tested ARCH=x86_64 with GCC 16.2.0, built out of tree with
make M=tools/testing/nvdimm:
tools/testing/nvdimm/test/ndtest.o

Assisted-by: LLM
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20261005155708.1471260-11-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

0 files changed, 0 insertions, 0 deletions