[PATCH] mailbox: bcm-pdc: Use scnprintf() for avoiding potential buffer overflow

[PATCH] mailbox: bcm-pdc: Use scnprintf() for avoiding potential buffer overflow

[Takashi Iwai]

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 drivers/mailbox/bcm-pdc-mailbox.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/mailbox/bcm-pdc-mailbox.c b/drivers/mailbox/bcm-pdc-mailbox.c
index fcb3b18a0678..c10a9318a4b7 100644
--- a/drivers/mailbox/bcm-pdc-mailbox.c
+++ b/drivers/mailbox/bcm-pdc-mailbox.c
@@ -436,33 +436,33 @@ static ssize_t pdc_debugfs_read(struct file *filp, char __user *ubuf,
 
 	pdcs = filp->private_data;
 	out_offset = 0;
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "SPU %u stats:\n", pdcs->pdc_idx);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "PDC requests....................%u\n",
 			       pdcs->pdc_requests);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "PDC responses...................%u\n",
 			       pdcs->pdc_replies);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "Tx not done.....................%u\n",
 			       pdcs->last_tx_not_done);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "Tx ring full....................%u\n",
 			       pdcs->tx_ring_full);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "Rx ring full....................%u\n",
 			       pdcs->rx_ring_full);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "Tx desc write fail. Ring full...%u\n",
 			       pdcs->txnobuf);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "Rx desc write fail. Ring full...%u\n",
 			       pdcs->rxnobuf);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "Receive overflow................%u\n",
 			       pdcs->rx_oflow);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
 			       "Num frags in rx ring............%u\n",
 			       NRXDACTIVE(pdcs->rxin, pdcs->last_rx_curr,
 					  pdcs->nrxpost));
-- 
2.16.4

Re: [PATCH] mailbox: bcm-pdc: Use scnprintf() for avoiding potential buffer overflow

[Takashi Iwai]

On Wed, 11 Mar 2020 08:45:13 +0100,
Takashi Iwai wrote:
> 
> Since snprintf() returns the would-be-output size instead of the
> actual output size, the succeeding calls may go beyond the given
> buffer limit.  Fix it by replacing with scnprintf().
> 
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

A gentle reminder for this forgotten patch.
Let me know if any further changes are needed.


thanks,

Takashi

> ---
>  drivers/mailbox/bcm-pdc-mailbox.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/mailbox/bcm-pdc-mailbox.c b/drivers/mailbox/bcm-pdc-mailbox.c
> index fcb3b18a0678..c10a9318a4b7 100644
> --- a/drivers/mailbox/bcm-pdc-mailbox.c
> +++ b/drivers/mailbox/bcm-pdc-mailbox.c
> @@ -436,33 +436,33 @@ static ssize_t pdc_debugfs_read(struct file *filp, char __user *ubuf,
>  
>  	pdcs = filp->private_data;
>  	out_offset = 0;
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "SPU %u stats:\n", pdcs->pdc_idx);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "PDC requests....................%u\n",
>  			       pdcs->pdc_requests);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "PDC responses...................%u\n",
>  			       pdcs->pdc_replies);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "Tx not done.....................%u\n",
>  			       pdcs->last_tx_not_done);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "Tx ring full....................%u\n",
>  			       pdcs->tx_ring_full);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "Rx ring full....................%u\n",
>  			       pdcs->rx_ring_full);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "Tx desc write fail. Ring full...%u\n",
>  			       pdcs->txnobuf);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "Rx desc write fail. Ring full...%u\n",
>  			       pdcs->rxnobuf);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "Receive overflow................%u\n",
>  			       pdcs->rx_oflow);
> -	out_offset += snprintf(buf + out_offset, out_count - out_offset,
> +	out_offset += scnprintf(buf + out_offset, out_count - out_offset,
>  			       "Num frags in rx ring............%u\n",
>  			       NRXDACTIVE(pdcs->rxin, pdcs->last_rx_curr,
>  					  pdcs->nrxpost));
> -- 
> 2.16.4
>