[PATCH v2] dev/parport: fix the array out-of-bounds risk

[tuhaowen]

Fixed array out-of-bounds issues caused by sprintf
by replacing it with snprintf for safer data copying,
ensuring the destination buffer is not overflowed.

Below is the stack trace I encountered during the actual issue:

[ 66.575408s] [pid:5118,cpu4,QThread,4]Kernel panic - not syncing: stack-protector:
Kernel stack is corrupted in: do_hardware_base_addr+0xcc/0xd0 [parport]
[ 66.575408s] [pid:5118,cpu4,QThread,5]CPU: 4 PID: 5118 Comm:
QThread Tainted: G S W O 5.10.97-arm64-desktop #7100.57021.2
[ 66.575439s] [pid:5118,cpu4,QThread,6]TGID: 5087 Comm: EFileApp
[ 66.575439s] [pid:5118,cpu4,QThread,7]Hardware name: HUAWEI HUAWEI QingYun
PGUX-W515x-B081/SP1PANGUXM, BIOS 1.00.07 04/29/2024
[ 66.575439s] [pid:5118,cpu4,QThread,8]Call trace:
[ 66.575469s] [pid:5118,cpu4,QThread,9] dump_backtrace+0x0/0x1c0
[ 66.575469s] [pid:5118,cpu4,QThread,0] show_stack+0x14/0x20
[ 66.575469s] [pid:5118,cpu4,QThread,1] dump_stack+0xd4/0x10c
[ 66.575500s] [pid:5118,cpu4,QThread,2] panic+0x1d8/0x3bc
[ 66.575500s] [pid:5118,cpu4,QThread,3] __stack_chk_fail+0x2c/0x38
[ 66.575500s] [pid:5118,cpu4,QThread,4] do_hardware_base_addr+0xcc/0xd0 [parport]

Signed-off-by: tuhaowen <tuhaowen@xxxxxxxxxxxxx>
---
Changes in v2:
- Replaced `sprintf` with `snprintf` to prevent array out-of-bounds issues.
- Link to v1: https://lore.kernel.org/all/20240626021136.12282-1-tuhaowen@xxxxxxxxxxxxx
---
 drivers/parport/procfs.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index bd388560ed59..c2e371c50dcf 100644
--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -51,12 +51,12 @@ static int do_active_device(struct ctl_table *table, int write,
 	
 	for (dev = port->devices; dev ; dev = dev->next) {
 		if(dev == port->cad) {
-			len += sprintf(buffer, "%s\n", dev->name);
+			len += snprintf(buffer, sizeof(buffer), "%s\n", dev->name);
 		}
 	}
 
 	if(!len) {
-		len += sprintf(buffer, "%s\n", "none");
+		len += snprintf(buffer, sizeof(buffer), "%s\n", "none");
 	}
 
 	if (len > *lenp)
@@ -87,19 +87,19 @@ static int do_autoprobe(struct ctl_table *table, int write,
 	}
 	
 	if ((str = info->class_name) != NULL)
-		len += sprintf (buffer + len, "CLASS:%s;\n", str);
+		len += snprintf (buffer + len, sizeof(buffer) - len, "CLASS:%s;\n", str);
 
 	if ((str = info->model) != NULL)
-		len += sprintf (buffer + len, "MODEL:%s;\n", str);
+		len += snprintf (buffer + len, sizeof(buffer) - len, "MODEL:%s;\n", str);
 
 	if ((str = info->mfr) != NULL)
-		len += sprintf (buffer + len, "MANUFACTURER:%s;\n", str);
+		len += snprintf (buffer + len, sizeof(buffer) - len, "MANUFACTURER:%s;\n", str);
 
 	if ((str = info->description) != NULL)
-		len += sprintf (buffer + len, "DESCRIPTION:%s;\n", str);
+		len += snprintf (buffer + len, sizeof(buffer) - len, "DESCRIPTION:%s;\n", str);
 
 	if ((str = info->cmdset) != NULL)
-		len += sprintf (buffer + len, "COMMAND SET:%s;\n", str);
+		len += snprintf (buffer + len, sizeof(buffer) - len, "COMMAND SET:%s;\n", str);
 
 	if (len > *lenp)
 		len = *lenp;
@@ -117,7 +117,7 @@ static int do_hardware_base_addr(struct ctl_table *table, int write,
 				 void *result, size_t *lenp, loff_t *ppos)
 {
 	struct parport *port = (struct parport *)table->extra1;
-	char buffer[20];
+	char buffer[64];
 	int len = 0;
 
 	if (*ppos) {
@@ -128,7 +128,7 @@ static int do_hardware_base_addr(struct ctl_table *table, int write,
 	if (write) /* permissions prevent this anyway */
 		return -EACCES;
 
-	len += sprintf (buffer, "%lu\t%lu\n", port->base, port->base_hi);
+	len += snprintf (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_table *table, int write,
 	if (write) /* permissions prevent this anyway */
 		return -EACCES;
 
-	len += sprintf (buffer, "%d\n", port->irq);
+	len += snprintf (buffer, sizeof(buffer), "%d\n", port->irq);
 
 	if (len > *lenp)
 		len = *lenp;
@@ -182,7 +182,7 @@ static int do_hardware_dma(struct ctl_table *table, int write,
 	if (write) /* permissions prevent this anyway */
 		return -EACCES;
 
-	len += sprintf (buffer, "%d\n", port->dma);
+	len += snprintf (buffer, sizeof(buffer), "%d\n", port->dma);
 
 	if (len > *lenp)
 		len = *lenp;
@@ -213,7 +213,7 @@ static int do_hardware_modes(struct ctl_table *table, int write,
 #define printmode(x)							\
 do {									\
 	if (port->modes & PARPORT_MODE_##x)				\
-		len += sprintf(buffer + len, "%s%s", f++ ? "," : "", #x); \
+		len += snprintf(buffer + len, sizeof(buffer) - len, "%s%s", f++ ? "," : "", #x); \
 } while (0)
 		int f = 0;
 		printmode(PCSPP);
-- 
2.20.1