linux-kernel - [PATCH v4] staging: wlan-ng: replace strncpy() with strscpy()

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Date:   Fri, 13 Oct 2023 12:54:26 +0300
From:   Calvince Otieno <calvncce@...il.com>
To:     outreachy@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Luke Koch <lu.ale.koch@...il.com>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Simon Horman <horms@...nel.org>,
        Calvince Otieno <calvncce@...il.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: [PATCH v4] staging: wlan-ng: replace  strncpy() with strscpy()

Checkpatch suggests the use of  strscpy() instead of strncpy().
The advantages are that it always adds a NUL terminator and it prevents
a read overflow if the src string is not properly terminated.  One
potential disadvantage is that it doesn't zero pad the string like
strncpy() does.

In this code, strscpy() and strncpy() are equivalent and it does not
affect runtime behavior.  The string is zeroed on the line before
using memset().  The resulting string was always NUL terminated and
PRISM2_USB_FWFILE is string literal "prism2_ru.fw" so it's NUL
terminated.

However, even though using strscpy() does not fix any bugs, it's
still nicer and makes checkpatch happy.

Signed-off-by: Calvince Otieno <calvncce@...il.com>
---
Patch version v4:
	Provide a valid description of the patch

Patch version v3:
        Correct the patch subject headline.
        staging: wlan-ng: remove strncpy() use in favor of strscpy()

Patch version v2 :
        Correct implementation of the strscpy()

drivers/staging/wlan-ng/prism2fw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/wlan-ng/prism2fw.c b/drivers/staging/wlan-ng/prism2fw.c
index 5d03b2b9aab4..3ccd11041646 100644
--- a/drivers/staging/wlan-ng/prism2fw.c
+++ b/drivers/staging/wlan-ng/prism2fw.c
@@ -725,7 +725,7 @@ static int plugimage(struct imgchunk *fchunk, unsigned int nfchunks,

                if (j == -1) {  /* plug the filename */
                        memset(dest, 0, s3plug[i].len);
-                       strncpy(dest, PRISM2_USB_FWFILE, s3plug[i].len - 1);
+                       strscpy(dest, PRISM2_USB_FWFILE, s3plug[i].len);
                } else {        /* plug a PDR */
                        memcpy(dest, &pda->rec[j]->data, s3plug[i].len);
                }

Patch version v1:
        Replacing strncpy() with strscpy()

 drivers/staging/wlan-ng/prism2fw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/wlan-ng/prism2fw.c b/drivers/staging/wlan-ng/prism2fw.c
index 5d03b2b9aab4..57a99dd12143 100644
--- a/drivers/staging/wlan-ng/prism2fw.c
+++ b/drivers/staging/wlan-ng/prism2fw.c
@@ -725,7 +725,7 @@ static int plugimage(struct imgchunk *fchunk, unsigned int nfchunks,

                if (j == -1) {  /* plug the filename */
                        memset(dest, 0, s3plug[i].len);
-                       strncpy(dest, PRISM2_USB_FWFILE, s3plug[i].len - 1);
+                       strscpy(dest, PRISM2_USB_FWFILE, s3plug[i].len - 1);
                } else {        /* plug a PDR */
                        memcpy(dest, &pda->rec[j]->data, s3plug[i].len);
                }

-- 
Calvince Otieno