net: ipconfig: Replace strncpy with strscpy in ic_proto_name

strncpy() is deprecated [1] for NUL-terminated destination buffers
because it does not guarantee NUL termination. Replace it with strscpy()
to ensure the destination buffer is always NUL-terminated and to avoid
any additional NUL padding.

Although the identifier buffer has 252 usable bytes, strncpy() copied
only up to 251 bytes to the zero-initialized buffer, relying on the last
byte to act as an implicit NUL terminator. Switching to strscpy() avoids
this implicit behavior and does not use magic numbers.

The source string is also NUL-terminated and satisfies the
__must_be_cstr() requirement of strscpy().

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20251126220804.102160-2-thorsten.blum@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index 22a7889876c1cf7d5233fe8a0ee12e134b20c1cd..019408d3ca2cb13d952c866b4a841add74d8ea7d 100644 (file)
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -1690,7 +1690,8 @@ static int __init ic_proto_name(char *name)
                        *v = 0;
                        if (kstrtou8(client_id, 0, dhcp_client_identifier))
                                pr_debug("DHCP: Invalid client identifier type\n");
-                       strncpy(dhcp_client_identifier + 1, v + 1, 251);
+                       strscpy(dhcp_client_identifier + 1, v + 1,
+                               sizeof(dhcp_client_identifier) - 1);
                        *v = ',';
                }
                return 1;