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[net-next,1/3] net: dsa: microchip: copy string using strscpy

Message ID 20241011-string-thing-v1-1-acc506568033@kernel.org (mailing list archive)
State New, archived
Headers show
Series net: String format safety updates | expand

Commit Message

Simon Horman Oct. 11, 2024, 9:57 a.m. UTC
Prior to this patch ksz_ptp_msg_irq_setup() uses snprintf() to copy
strings. It does so by passing strings as the format argument of
snprintf(). This appears to be safe, due to the absence of format
specifiers in the strings, which are declared within the same function.
But nonetheless GCC 14 warns about it:

.../ksz_ptp.c:1109:55: warning: format string is not a string literal (potentially insecure) [-Wformat-security]
 1109 |         snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
      |                                                              ^~~~~~~
.../ksz_ptp.c:1109:55: note: treat the string as an argument to avoid this
 1109 |         snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
      |                                                              ^
      |                                                              "%s",

As what we are really dealing with here is a string copy, it seems make
sense to use a function designed for this purpose. In this case null
padding is not required, so strscpy is appropriate. And as the
destination is an array, the 2-argument variant may be used.

Signed-off-by: Simon Horman <horms@kernel.org>
---
 drivers/net/dsa/microchip/ksz_ptp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Daniel Machon Oct. 13, 2024, 9:52 a.m. UTC | #1
> Prior to this patch ksz_ptp_msg_irq_setup() uses snprintf() to copy
> strings. It does so by passing strings as the format argument of
> snprintf(). This appears to be safe, due to the absence of format
> specifiers in the strings, which are declared within the same function.
> But nonetheless GCC 14 warns about it:
> 
> .../ksz_ptp.c:1109:55: warning: format string is not a string literal (potentially insecure) [-Wformat-security]
>  1109 |         snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
>       |                                                              ^~~~~~~
> .../ksz_ptp.c:1109:55: note: treat the string as an argument to avoid this
>  1109 |         snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
>       |                                                              ^
>       |                                                              "%s",
> 
> As what we are really dealing with here is a string copy, it seems make
> sense to use a function designed for this purpose. In this case null
> padding is not required, so strscpy is appropriate. And as the
> destination is an array, the 2-argument variant may be used.

.. is an array - and of fixed size.

> 
> Signed-off-by: Simon Horman <horms@kernel.org>
> ---
>  drivers/net/dsa/microchip/ksz_ptp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/microchip/ksz_ptp.c b/drivers/net/dsa/microchip/ksz_ptp.c
> index 050f17c43ef6..22fb9ef4645c 100644
> --- a/drivers/net/dsa/microchip/ksz_ptp.c
> +++ b/drivers/net/dsa/microchip/ksz_ptp.c
> @@ -1106,7 +1106,7 @@ static int ksz_ptp_msg_irq_setup(struct ksz_port *port, u8 n)
>         ptpmsg_irq->port = port;
>         ptpmsg_irq->ts_reg = ops->get_port_addr(port->num, ts_reg[n]);
> 
> -       snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
> +       strscpy(ptpmsg_irq->name, name[n]);
> 
>         ptpmsg_irq->num = irq_find_mapping(port->ptpirq.domain, n);
>         if (ptpmsg_irq->num < 0)
> 
> --
> 2.45.2
>

This looks good to me.

Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
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Patch

diff --git a/drivers/net/dsa/microchip/ksz_ptp.c b/drivers/net/dsa/microchip/ksz_ptp.c
index 050f17c43ef6..22fb9ef4645c 100644
--- a/drivers/net/dsa/microchip/ksz_ptp.c
+++ b/drivers/net/dsa/microchip/ksz_ptp.c
@@ -1106,7 +1106,7 @@  static int ksz_ptp_msg_irq_setup(struct ksz_port *port, u8 n)
 	ptpmsg_irq->port = port;
 	ptpmsg_irq->ts_reg = ops->get_port_addr(port->num, ts_reg[n]);
 
-	snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
+	strscpy(ptpmsg_irq->name, name[n]);
 
 	ptpmsg_irq->num = irq_find_mapping(port->ptpirq.domain, n);
 	if (ptpmsg_irq->num < 0)