[PATCH 7/7] nvdimm: ndtest: Return the string length from flags_show()

[PATCH 7/7] nvdimm: ndtest: Return the string length from flags_show()

[Kees Cook]

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
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <iweiny@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Guangshuo Li <lgs201920130244@gmail.com>
Cc: <nvdimm@lists.linux.dev>
---
 tools/testing/nvdimm/test/ndtest.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/nvdimm/test/ndtest.c b/tools/testing/nvdimm/test/ndtest.c
index 2051ad5d4882..f097f2992966 100644
--- a/tools/testing/nvdimm/test/ndtest.c
+++ b/tools/testing/nvdimm/test/ndtest.c
@@ -693,7 +693,7 @@ static ssize_t flags_show(struct device *dev,
 	if (seq_buf_used(&s))
 		seq_buf_printf(&s, "\n");
 
-	return seq_buf_used(&s);
+	return seq_buf_strlen(&s);
 }
 static DEVICE_ATTR_RO(flags);
 
-- 
2.34.1

Re: [PATCH 7/7] nvdimm: ndtest: Return the string length from flags_show()

[Dave Jiang]

On 9/16/26 5:23 PM, Kees Cook wrote:
> 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
> Signed-off-by: Kees Cook <kees@kernel.org>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
> Cc: Alison Schofield <alison.schofield@intel.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Ira Weiny <iweiny@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Cc: Guangshuo Li <lgs201920130244@gmail.com>
> Cc: <nvdimm@lists.linux.dev>
> ---
>  tools/testing/nvdimm/test/ndtest.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/nvdimm/test/ndtest.c b/tools/testing/nvdimm/test/ndtest.c
> index 2051ad5d4882..f097f2992966 100644
> --- a/tools/testing/nvdimm/test/ndtest.c
> +++ b/tools/testing/nvdimm/test/ndtest.c
> @@ -693,7 +693,7 @@ static ssize_t flags_show(struct device *dev,
>  	if (seq_buf_used(&s))
>  		seq_buf_printf(&s, "\n");
>  
> -	return seq_buf_used(&s);
> +	return seq_buf_strlen(&s);
>  }
>  static DEVICE_ATTR_RO(flags);
>