[PATCH 5.10 41/52] parport: Proper fix for array out-of-bounds access

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 02ac3a9ef3a18b58d8f3ea2b6e46de657bf6c4f9 upstream.

The recent fix for array out-of-bounds accesses replaced sprintf()
calls blindly with snprintf().  However, since snprintf() returns the
would-be-printed size, not the actually output size, the length
calculation can still go over the given limit.

Use scnprintf() instead of snprintf(), which returns the actually
output letters, for addressing the potential out-of-bounds access
properly.

Fixes: ab11dac93d2d ("dev/parport: fix the array out-of-bounds risk")
Cc: stable@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20240920103318.19271-1-tiwai@suse.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/parport/procfs.c |   22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -51,12 +51,12 @@ static int do_active_device(struct ctl_t
 	
 	for (dev = port->devices; dev ; dev = dev->next) {
 		if(dev == port->cad) {
-			len += snprintf(buffer, sizeof(buffer), "%s\n", dev->name);
+			len += scnprintf(buffer, sizeof(buffer), "%s\n", dev->name);
 		}
 	}
 
 	if(!len) {
-		len += snprintf(buffer, sizeof(buffer), "%s\n", "none");
+		len += scnprintf(buffer, sizeof(buffer), "%s\n", "none");
 	}
 
 	if (len > *lenp)
@@ -87,19 +87,19 @@ static int do_autoprobe(struct ctl_table
 	}
 	
 	if ((str = info->class_name) != NULL)
-		len += snprintf (buffer + len, sizeof(buffer) - len, "CLASS:%s;\n", str);
+		len += scnprintf (buffer + len, sizeof(buffer) - len, "CLASS:%s;\n", str);
 
 	if ((str = info->model) != NULL)
-		len += snprintf (buffer + len, sizeof(buffer) - len, "MODEL:%s;\n", str);
+		len += scnprintf (buffer + len, sizeof(buffer) - len, "MODEL:%s;\n", str);
 
 	if ((str = info->mfr) != NULL)
-		len += snprintf (buffer + len, sizeof(buffer) - len, "MANUFACTURER:%s;\n", str);
+		len += scnprintf (buffer + len, sizeof(buffer) - len, "MANUFACTURER:%s;\n", str);
 
 	if ((str = info->description) != NULL)
-		len += snprintf (buffer + len, sizeof(buffer) - len, "DESCRIPTION:%s;\n", str);
+		len += scnprintf (buffer + len, sizeof(buffer) - len, "DESCRIPTION:%s;\n", str);
 
 	if ((str = info->cmdset) != NULL)
-		len += snprintf (buffer + len, sizeof(buffer) - len, "COMMAND SET:%s;\n", str);
+		len += scnprintf (buffer + len, sizeof(buffer) - len, "COMMAND SET:%s;\n", str);
 
 	if (len > *lenp)
 		len = *lenp;
@@ -128,7 +128,7 @@ static int do_hardware_base_addr(struct
 	if (write) /* permissions prevent this anyway */
 		return -EACCES;
 
-	len += snprintf (buffer, sizeof(buffer), "%lu\t%lu\n", port->base, port->base_hi);
+	len += scnprintf (buffer, sizeof(buffer), "%lu\t%lu\n", port->base, port->base_hi);
 
 	if (len > *lenp)
 		len = *lenp;
@@ -155,7 +155,7 @@ static int do_hardware_irq(struct ctl_ta
 	if (write) /* permissions prevent this anyway */
 		return -EACCES;
 
-	len += snprintf (buffer, sizeof(buffer), "%d\n", port->irq);
+	len += scnprintf (buffer, sizeof(buffer), "%d\n", port->irq);
 
 	if (len > *lenp)
 		len = *lenp;
@@ -182,7 +182,7 @@ static int do_hardware_dma(struct ctl_ta
 	if (write) /* permissions prevent this anyway */
 		return -EACCES;
 
-	len += snprintf (buffer, sizeof(buffer), "%d\n", port->dma);
+	len += scnprintf (buffer, sizeof(buffer), "%d\n", port->dma);
 
 	if (len > *lenp)
 		len = *lenp;
@@ -213,7 +213,7 @@ static int do_hardware_modes(struct ctl_
 #define printmode(x)							\
 do {									\
 	if (port->modes & PARPORT_MODE_##x)				\
-		len += snprintf(buffer + len, sizeof(buffer) - len, "%s%s", f++ ? "," : "", #x); \
+		len += scnprintf(buffer + len, sizeof(buffer) - len, "%s%s", f++ ? "," : "", #x); \
 } while (0)
 		int f = 0;
 		printmode(PCSPP);