[PATCH v3 10/11] nvdimm: ndtest: Return the string length from flags_show()

[PATCH v3 10/11] 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
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Kees Cook <kees@kernel.org>
---
 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 v3 10/11] nvdimm: ndtest: Return the string length from flags_show()

[Alison Schofield]

On Wed, Sep 30, 2026 at 04:52:38PM -0700, 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
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Signed-off-by: Kees Cook <kees@kernel.org>


Hi Kees,

Should I include this one in a 7.4 PR for nvdimm or is someone else
merging the entire series?

-- Alison



> ---
>  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 v3 10/11] nvdimm: ndtest: Return the string length from flags_show()

[Alison Schofield]

On Wed, Sep 30, 2026 at 10:40:47PM -0700, Alison Schofield wrote:
> On Wed, Sep 30, 2026 at 04:52:38PM -0700, 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
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> > Signed-off-by: Kees Cook <kees@kernel.org>
> 
> 
> Hi Kees,
> 
> Should I include this one in a 7.4 PR for nvdimm or is someone else
> merging the entire series?

NVM, found my answer when trying to build without the entire series.
Tagging but won't try to merge - 

Reviewed-by: Alison Schofield <alison.schofield@intel.com>

> 
> -- Alison
> 
> 
> 
> > ---
> >  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 v3 10/11] nvdimm: ndtest: Return the string length from flags_show()

[Kees Cook]

On Thu, Oct 01, 2026 at 04:39:57PM -0700, Alison Schofield wrote:
> > Should I include this one in a 7.4 PR for nvdimm or is someone else
> > merging the entire series?
>
> NVM, found my answer when trying to build without the entire series.
> Tagging but won't try to merge -

Right, it needs seq_buf_strlen() from earlier in the series, so I'll
take the whole series through my tree. Thanks for the review!

-Kees

-- 
Kees Cook