s390/hmcdrv: Manual replacement of the deprecated strlcpy() with retu…

…rn values

The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.
It can lead to linear read overflows, crashes, etc...

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@gmail.com>

drivers/s390/char/diag_ftp.c

@@ -158,8 +158,8 @@ ssize_t diag_ftp_cmd(const struct hmcdrv_ftp_cmdspec *ftp, size_t *fsize)
 		goto out;
 	}
 
-	len = strlcpy(ldfpl->fident, ftp->fname, sizeof(ldfpl->fident));
-	if (len >= HMCDRV_FTP_FIDENT_MAX) {
+	len = strscpy(ldfpl->fident, ftp->fname, sizeof(ldfpl->fident));
+	if (len == -E2BIG) {
 		len = -EINVAL;
 		goto out_free;
 	}

drivers/s390/char/sclp_ftp.c

@@ -87,7 +87,7 @@ static int sclp_ftp_et7(const struct hmcdrv_ftp_cmdspec *ftp)
 	struct completion completion;
 	struct sclp_diag_sccb *sccb;
 	struct sclp_req *req;
-	size_t len;
+	ssize_t len;
 	int rc;
 
 	req = kzalloc(sizeof(*req), GFP_KERNEL);
@@ -114,9 +114,9 @@ static int sclp_ftp_et7(const struct hmcdrv_ftp_cmdspec *ftp)
 	sccb->evbuf.mdd.ftp.length = ftp->len;
 	sccb->evbuf.mdd.ftp.bufaddr = virt_to_phys(ftp->buf);
 
-	len = strlcpy(sccb->evbuf.mdd.ftp.fident, ftp->fname,
+	len = strscpy(sccb->evbuf.mdd.ftp.fident, ftp->fname,
 		      HMCDRV_FTP_FIDENT_MAX);
-	if (len >= HMCDRV_FTP_FIDENT_MAX) {
+	if (len == -E2BIG) {
 		rc = -EINVAL;
 		goto out_free;
 	}