[PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[Mariia Nikitash]

In preparation for removing the deprecated strlcat() API[1],
replace the strscpy() and strlcat() calls with a single snprintf()
call to construct the IR device path.

Both the source and destination buffers have the same capacity,
and the return values are unused. This preserves the resulting
string, including truncation behavior.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>
---
 drivers/media/common/siano/smsir.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/common/siano/smsir.c b/drivers/media/common/siano/smsir.c
index 283770d583d5..636ff228108b 100644
--- a/drivers/media/common/siano/smsir.c
+++ b/drivers/media/common/siano/smsir.c
@@ -55,8 +55,8 @@ int sms_ir_init(struct smscore_device_t *coredev)
 	snprintf(coredev->ir.name, sizeof(coredev->ir.name),
 		 "SMS IR (%s)", sms_get_board(board_id)->name);
 
-	strscpy(coredev->ir.phys, coredev->devpath, sizeof(coredev->ir.phys));
-	strlcat(coredev->ir.phys, "/ir0", sizeof(coredev->ir.phys));
+	snprintf(coredev->ir.phys, sizeof(coredev->ir.phys),
+		 "%s/ir0", coredev->devpath);
 
 	dev->device_name = coredev->ir.name;
 	dev->input_phys = coredev->ir.phys;
-- 
2.43.0

Re: [PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[Alejandro Colomar]

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Hi Mariia,

> Date: 2026-11-04 01:02:39-0800
> From: Mariia Nikitash <nikitash.mariiaw@gmail.com>
>
> In preparation for removing the deprecated strlcat() API[1],
> replace the strscpy() and strlcat() calls with a single snprintf()
> call to construct the IR device path.
> 
> Both the source and destination buffers have the same capacity,

The line above seems irrelevant, and potentially confusing.
The size of the input is not important, because since we're appending
stuff after it, truncation may actually happen.

> and the return values are unused. This preserves the resulting
> string, including truncation behavior.
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>

Except for the small comment above,

Reviewed-by: Alejandro Colomar <alx@kernel.org>


Cheers,
Alex

> ---
>  drivers/media/common/siano/smsir.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/common/siano/smsir.c b/drivers/media/common/siano/smsir.c
> index 283770d583d5..636ff228108b 100644
> --- a/drivers/media/common/siano/smsir.c
> +++ b/drivers/media/common/siano/smsir.c
> @@ -55,8 +55,8 @@ int sms_ir_init(struct smscore_device_t *coredev)
>  	snprintf(coredev->ir.name, sizeof(coredev->ir.name),
>  		 "SMS IR (%s)", sms_get_board(board_id)->name);
>  
> -	strscpy(coredev->ir.phys, coredev->devpath, sizeof(coredev->ir.phys));
> -	strlcat(coredev->ir.phys, "/ir0", sizeof(coredev->ir.phys));
> +	snprintf(coredev->ir.phys, sizeof(coredev->ir.phys),
> +		 "%s/ir0", coredev->devpath);
>  
>  	dev->device_name = coredev->ir.name;
>  	dev->input_phys = coredev->ir.phys;
> -- 
> 2.43.0
> 
> 

-- 
<https://www.alejandro-colomar.es>

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Re: [PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[Mariia Nikitash]

On Wed, Nov 4, 2026 at 3:25 AM Alejandro Colomar
<alx+linux-hardening@kernel.org> wrote:
>
> Hi Mariia,

Hi Alejandro,

>
> > Date: 2026-11-04 01:02:39-0800
> > From: Mariia Nikitash <nikitash.mariiaw@gmail.com>
> >
> > In preparation for removing the deprecated strlcat() API[1],
> > replace the strscpy() and strlcat() calls with a single snprintf()
> > call to construct the IR device path.
> >
> > Both the source and destination buffers have the same capacity,
>
> The line above seems irrelevant, and potentially confusing.
> The size of the input is not important, because since we're appending
> stuff after it, truncation may actually happen.

Agreed. I've removed the statement about buffer capacities from the
commit message in v2. No code changes.


>
> > and the return values are unused. This preserves the resulting
> > string, including truncation behavior.
> >
> > Link: https://github.com/KSPP/linux/issues/370 [1]
> > Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>
>
> Except for the small comment above,
>
> Reviewed-by: Alejandro Colomar <alx@kernel.org>
>

Thanks for the review!

>
> Cheers,
> Alex
>

Best,
Mariia


> > ---
> >  drivers/media/common/siano/smsir.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/common/siano/smsir.c b/drivers/media/common/siano/smsir.c
> > index 283770d583d5..636ff228108b 100644
> > --- a/drivers/media/common/siano/smsir.c
> > +++ b/drivers/media/common/siano/smsir.c
> > @@ -55,8 +55,8 @@ int sms_ir_init(struct smscore_device_t *coredev)
> >       snprintf(coredev->ir.name, sizeof(coredev->ir.name),
> >                "SMS IR (%s)", sms_get_board(board_id)->name);
> >
> > -     strscpy(coredev->ir.phys, coredev->devpath, sizeof(coredev->ir.phys));
> > -     strlcat(coredev->ir.phys, "/ir0", sizeof(coredev->ir.phys));
> > +     snprintf(coredev->ir.phys, sizeof(coredev->ir.phys),
> > +              "%s/ir0", coredev->devpath);
> >
> >       dev->device_name = coredev->ir.name;
> >       dev->input_phys = coredev->ir.phys;
> > --
> > 2.43.0
> >
> >
>
> --
> <https://www.alejandro-colomar.es>

Re: [PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[David Laight]

On Wed, 4 Nov 2026 12:25:17 +0100
Alejandro Colomar <alx+linux-hardening@kernel.org> wrote:

> Hi Mariia,
> 
> > Date: 2026-11-04 01:02:39-0800
> > From: Mariia Nikitash <nikitash.mariiaw@gmail.com>
> >
> > In preparation for removing the deprecated strlcat() API[1],
> > replace the strscpy() and strlcat() calls with a single snprintf()
> > call to construct the IR device path.
> > 
> > Both the source and destination buffers have the same capacity,  
> 
> The line above seems irrelevant, and potentially confusing.
> The size of the input is not important, because since we're appending
> stuff after it, truncation may actually happen.

And gcc's stupid format overflow check is going to complain.

David

> 
> > and the return values are unused. This preserves the resulting
> > string, including truncation behavior.
> > 
> > Link: https://github.com/KSPP/linux/issues/370 [1]
> > Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>  
> 
> Except for the small comment above,
> 
> Reviewed-by: Alejandro Colomar <alx@kernel.org>
> 
> 
> Cheers,
> Alex
> 
> > ---
> >  drivers/media/common/siano/smsir.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/media/common/siano/smsir.c b/drivers/media/common/siano/smsir.c
> > index 283770d583d5..636ff228108b 100644
> > --- a/drivers/media/common/siano/smsir.c
> > +++ b/drivers/media/common/siano/smsir.c
> > @@ -55,8 +55,8 @@ int sms_ir_init(struct smscore_device_t *coredev)
> >  	snprintf(coredev->ir.name, sizeof(coredev->ir.name),
> >  		 "SMS IR (%s)", sms_get_board(board_id)->name);
> >  
> > -	strscpy(coredev->ir.phys, coredev->devpath, sizeof(coredev->ir.phys));
> > -	strlcat(coredev->ir.phys, "/ir0", sizeof(coredev->ir.phys));
> > +	snprintf(coredev->ir.phys, sizeof(coredev->ir.phys),
> > +		 "%s/ir0", coredev->devpath);
> >  
> >  	dev->device_name = coredev->ir.name;
> >  	dev->input_phys = coredev->ir.phys;
> > -- 
> > 2.43.0
> > 
> >   
> 

Re: [PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[Mariia Nikitash]

On Thu, Nov 5, 2026 at 3:32 AM David Laight
<david.laight.linux@gmail.com> wrote:
>
> On Wed, 4 Nov 2026 12:25:17 +0100
> Alejandro Colomar <alx+linux-hardening@kernel.org> wrote:
>
> > Hi Mariia,
> >
> > > Date: 2026-11-04 01:02:39-0800
> > > From: Mariia Nikitash <nikitash.mariiaw@gmail.com>
> > >
> > > In preparation for removing the deprecated strlcat() API[1],
> > > replace the strscpy() and strlcat() calls with a single snprintf()
> > > call to construct the IR device path.
> > >
> > > Both the source and destination buffers have the same capacity,
> >
> > The line above seems irrelevant, and potentially confusing.
> > The size of the input is not important, because since we're appending
> > stuff after it, truncation may actually happen.
>
> And gcc's stupid format overflow check is going to complain.

Thanks for pointing this out! I initially tested with Clang, but
reproduced the warning with GCC. I've switched to seq_buf for v3.

>
> David
>

Best,
Mariia

> >
> > > and the return values are unused. This preserves the resulting
> > > string, including truncation behavior.
> > >
> > > Link: https://github.com/KSPP/linux/issues/370 [1]
> > > Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>
> >
> > Except for the small comment above,
> >
> > Reviewed-by: Alejandro Colomar <alx@kernel.org>
> >
> >
> > Cheers,
> > Alex
> >
> > > ---
> > >  drivers/media/common/siano/smsir.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/media/common/siano/smsir.c b/drivers/media/common/siano/smsir.c
> > > index 283770d583d5..636ff228108b 100644
> > > --- a/drivers/media/common/siano/smsir.c
> > > +++ b/drivers/media/common/siano/smsir.c
> > > @@ -55,8 +55,8 @@ int sms_ir_init(struct smscore_device_t *coredev)
> > >     snprintf(coredev->ir.name, sizeof(coredev->ir.name),
> > >              "SMS IR (%s)", sms_get_board(board_id)->name);
> > >
> > > -   strscpy(coredev->ir.phys, coredev->devpath, sizeof(coredev->ir.phys));
> > > -   strlcat(coredev->ir.phys, "/ir0", sizeof(coredev->ir.phys));
> > > +   snprintf(coredev->ir.phys, sizeof(coredev->ir.phys),
> > > +            "%s/ir0", coredev->devpath);
> > >
> > >     dev->device_name = coredev->ir.name;
> > >     dev->input_phys = coredev->ir.phys;
> > > --
> > > 2.43.0
> > >
> > >
> >
>

Re: [PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[David Laight]

On Thu, 5 Nov 2026 17:44:00 -0800
Mariia Nikitash <nikitash.mariiaw@gmail.com> wrote:

> On Thu, Nov 5, 2026 at 3:32 AM David Laight <david.laight.linux@gmail.com>
> wrote:
> >
> > On Wed, 4 Nov 2026 12:25:17 +0100
> > Alejandro Colomar <alx+linux-hardening@kernel.org> wrote:
> >  
> > > Hi Mariia,
> > >  
> > > > Date: 2026-11-04 01:02:39-0800
> > > > From: Mariia Nikitash <nikitash.mariiaw@gmail.com>
> > > >
> > > > In preparation for removing the deprecated strlcat() API[1],
> > > > replace the strscpy() and strlcat() calls with a single snprintf()
> > > > call to construct the IR device path.
> > > >
> > > > Both the source and destination buffers have the same capacity,  
> > >
> > > The line above seems irrelevant, and potentially confusing.
> > > The size of the input is not important, because since we're appending
> > > stuff after it, truncation may actually happen.  
> >
> > And gcc's stupid format overflow check is going to complain.  
> 
> Thanks for pointing this out! I initially tested with Clang, but reproduced
> the warning with GCC. I've switched to seq_buf for v3.

That is entirely OTT.
Currently scnprintf() doesn't complain.

David

> 
> >
> > David
> >  
> 
> Best,
> Mariia
> 
> 
> > >  
> > > > and the return values are unused. This preserves the resulting
> > > > string, including truncation behavior.
> > > >
> > > > Link: https://github.com/KSPP/linux/issues/370 [1]
> > > > Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>  
> > >
> > > Except for the small comment above,
> > >
> > > Reviewed-by: Alejandro Colomar <alx@kernel.org>
> > >
> > >
> > > Cheers,
> > > Alex
> > >  
> > > > ---
> > > >  drivers/media/common/siano/smsir.c | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/media/common/siano/smsir.c  
> b/drivers/media/common/siano/smsir.c
> > > > index 283770d583d5..636ff228108b 100644
> > > > --- a/drivers/media/common/siano/smsir.c
> > > > +++ b/drivers/media/common/siano/smsir.c
> > > > @@ -55,8 +55,8 @@ int sms_ir_init(struct smscore_device_t *coredev)
> > > >     snprintf(coredev->ir.name, sizeof(coredev->ir.name),
> > > >              "SMS IR (%s)", sms_get_board(board_id)->name);
> > > >
> > > > -   strscpy(coredev->ir.phys, coredev->devpath,  
> sizeof(coredev->ir.phys));
> > > > -   strlcat(coredev->ir.phys, "/ir0", sizeof(coredev->ir.phys));
> > > > +   snprintf(coredev->ir.phys, sizeof(coredev->ir.phys),
> > > > +            "%s/ir0", coredev->devpath);
> > > >
> > > >     dev->device_name = coredev->ir.name;
> > > >     dev->input_phys = coredev->ir.phys;
> > > > --
> > > > 2.43.0
> > > >
> > > >  
> > >  
> >  

Re: [PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[Kees Cook]

On November 6, 2026 2:27:23 AM PST, David Laight <david.laight.linux@gmail.com> wrote:
>On Thu, 5 Nov 2026 17:44:00 -0800
>Mariia Nikitash <nikitash.mariiaw@gmail.com> wrote:
>
>> On Thu, Nov 5, 2026 at 3:32 AM David Laight <david.laight.linux@gmail.com>
>> wrote:
>> >
>> > On Wed, 4 Nov 2026 12:25:17 +0100
>> > Alejandro Colomar <alx+linux-hardening@kernel.org> wrote:
>> >  
>> > > Hi Mariia,
>> > >  
>> > > > Date: 2026-11-04 01:02:39-0800
>> > > > From: Mariia Nikitash <nikitash.mariiaw@gmail.com>
>> > > >
>> > > > In preparation for removing the deprecated strlcat() API[1],
>> > > > replace the strscpy() and strlcat() calls with a single snprintf()
>> > > > call to construct the IR device path.
>> > > >
>> > > > Both the source and destination buffers have the same capacity,  
>> > >
>> > > The line above seems irrelevant, and potentially confusing.
>> > > The size of the input is not important, because since we're appending
>> > > stuff after it, truncation may actually happen.  
>> >
>> > And gcc's stupid format overflow check is going to complain.  
>> 
>> Thanks for pointing this out! I initially tested with Clang, but reproduced
>> the warning with GCC. I've switched to seq_buf for v3.
>
>That is entirely OTT.
>Currently scnprintf() doesn't complain.


What does GCC say about it? Is it mad about src >= dest length but the format adds chars?

I agree that seq_buf isn't needed here; that's really only for complicated cases where the simpler solutions don't fit. (In this case, snprintf-like is best.)

Both seq_buf and scnprintf avoid the warning because GCC just happens to not recognize the pattern when using those helpers, so this is just silencing the warning, much like strlcat() did too.

Truncation was the norm already, so scnprintf is probably the best fit, but I think it may be worth looking at the surrounding code and conventions to decide if truncation should be communicated upward to the caller (i.e. fail), or if the structures involved should be adjusted to avoid truncation chance, etc etc. If possible we should avoid the weakness, but if not, just use the minimal solution here, which is scnprintf, though that kicks the warning down the road...

-Kees


-- 
Kees Cook

Re: [PATCH] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[Shihuang Liu]

On Wed, Nov 04, 2026 at 01:02:39AM -0800, Mariia Nikitash wrote:
> In preparation for removing the deprecated strlcat() API[1],
> replace the strscpy() and strlcat() calls with a single snprintf()
> call to construct the IR device path.
> 
> Both the source and destination buffers have the same capacity,
> and the return values are unused. This preserves the resulting
> string, including truncation behavior.
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>

Reviewed-by: Shihuang Liu <shlomojune6@gmail.com>

[PATCH v2] media: siano: Replace strlcat() with snprintf() in sms_ir_init()

[Mariia Nikitash]

In preparation for removing the deprecated strlcat() API[1],
replace the strscpy() and strlcat() calls with a single snprintf()
call to construct the IR device path.

The return values are unused. This preserves the resulting
string, including truncation behavior.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Mariia Nikitash <nikitash.mariiaw@gmail.com>
Reviewed-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Shihuang Liu <shlomojune6@gmail.com>
---

Changes in v2:
- No code changes.
- Remove the statement about buffer capacities
  from the commit message.
- Add Reviewed-by tags from Alejandro Colomar and Shihuang Liu.

 drivers/media/common/siano/smsir.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/common/siano/smsir.c b/drivers/media/common/siano/smsir.c
index 283770d583d5..636ff228108b 100644
--- a/drivers/media/common/siano/smsir.c
+++ b/drivers/media/common/siano/smsir.c
@@ -55,8 +55,8 @@ int sms_ir_init(struct smscore_device_t *coredev)
 	snprintf(coredev->ir.name, sizeof(coredev->ir.name),
 		 "SMS IR (%s)", sms_get_board(board_id)->name);
 
-	strscpy(coredev->ir.phys, coredev->devpath, sizeof(coredev->ir.phys));
-	strlcat(coredev->ir.phys, "/ir0", sizeof(coredev->ir.phys));
+	snprintf(coredev->ir.phys, sizeof(coredev->ir.phys),
+		 "%s/ir0", coredev->devpath);
 
 	dev->device_name = coredev->ir.name;
 	dev->input_phys = coredev->ir.phys;
-- 
2.43.0