netdev - [PATCH ethtool] netlink: fix print_string when the value is NULL

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Message-ID: <aILUS-BlVm5tubAF@maurice.local>
Date: Thu, 24 Jul 2025 19:48:11 -0500
From: Michel Lind <michel@...hel-slm.name>
To: Michal Kubecek <mkubecek@...e.cz>
Cc: netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH ethtool] netlink: fix print_string when the value is NULL

The previous fix in commit b70c92866102 ("netlink: fix missing headers
in text output") handles the case when value is NULL by still using
`fprintf` but passing no value.

This fails if `-Werror=format-security` is passed to gcc, as is the
default in distros like Fedora.

```
json_print.c: In function 'print_string':
json_print.c:147:25: error: format not a string literal and no format arguments [-Werror=format-security]
  147 |                         fprintf(stdout, fmt);
      |
```

Use `fprintf(stdout, "%s", fmt)` instead, using the format string as the
value, since in this case we know it is just a string without format
chracters.

Reviewed-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Michel Lind <michel@...hel-slm.name>
---
 json_print.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/json_print.c b/json_print.c
index e07c651..75e6cd9 100644
--- a/json_print.c
+++ b/json_print.c
@@ -144,7 +144,7 @@ void print_string(enum output_type type,
 		if (value)
 			fprintf(stdout, fmt, value);
 		else
-			fprintf(stdout, fmt);
+			fprintf(stdout, "%s", fmt);
 	}
 }
 
-- 
2.50.1


-- 
 _o) Michel Lind
_( ) identities: https://keyoxide.org/5dce2e7e9c3b1cffd335c1d78b229d2f7ccc04f2
     README:     https://fedoraproject.org/wiki/User:Salimma#README

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