[PATCH v2] nfc: pn544: i2c: Replace strcpy() with strscpy()

[tomasz . unger]

From: Tomasz Unger <tomasz.unger@xxxxxxxx>

strcpy() does not limit the number of bytes copied which can lead to
buffer overflow when firmware_name is derived from user input via
NFC subsystem. This is a bug fix, not a cleanup.

Replace with strscpy() which limits the copy to the size of the
destination buffer. Since phy->firmware_name is an array, the
two-argument variant of strscpy() is used - the compiler deduces
the buffer size automatically.

Fixes: 06c660340f1e ("NFC: pn544: i2c: Add firmware download implementation for pn544")
Signed-off-by: Tomasz Unger <tomasz.unger@xxxxxxxx>
---
Changes since v1 (requested by Simon Horman <horms@xxxxxxxxxx>):
- Use two-argument strscpy() since phy->firmware_name is an array
    
Testing:
- checkpatch.pl: 0 errors, 0 warnings
- make drivers/nfc/pn544/: compiled successfully, 0 errors, 0 warnings
- Module loaded successfully in QEMU (x86_64) with buildroot:
  insmod pn544.ko - no errors, confirmed via lsmod

 drivers/nfc/pn544/i2c.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nfc/pn544/i2c.c b/drivers/nfc/pn544/i2c.c
index a0dfb3f98d5a..b31b5bef7187 100644
--- a/drivers/nfc/pn544/i2c.c
+++ b/drivers/nfc/pn544/i2c.c
@@ -526,7 +526,7 @@ static int pn544_hci_i2c_fw_download(void *phy_id, const char *firmware_name,
 
 	pr_info("Starting Firmware Download (%s)\n", firmware_name);
 
-	strcpy(phy->firmware_name, firmware_name);
+	strscpy(phy->firmware_name, firmware_name);
 
 	phy->hw_variant = hw_variant;
 	phy->fw_work_state = FW_WORK_STATE_START;
-- 
2.53.0