net: ipconfig: Don't override command-line hostnames or domains

BugLink: https://bugs.launchpad.net/bugs/1936688
[ Upstream commit b508d5fb69c2211a1b860fc058aafbefc3b3c3cd ]

If the user specifies a hostname or domain name as part of the ip=
command-line option, preserve it and don't overwrite it with one
supplied by DHCP/BOOTP.

For instance, ip=::::myhostname::dhcp will use "myhostname" rather than
ignoring and overwriting it.

Fix the comment on ic_bootp_string that suggests it only copies a string
"if not already set"; it doesn't have any such logic.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index 3cd13e1bc6a7009255a3aea0cf668c0142ae0022..213a1c91507d94975cfdc15ad7b6dfc0800517d6 100644 (file)
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -870,7 +870,7 @@ static void __init ic_bootp_send_if(struct ic_device *d, unsigned long jiffies_d
 
 
 /*
- *  Copy BOOTP-supplied string if not already set.
+ *  Copy BOOTP-supplied string
  */
 static int __init ic_bootp_string(char *dest, char *src, int len, int max)
 {
@@ -919,12 +919,15 @@ static void __init ic_do_bootp_ext(u8 *ext)
                }
                break;
        case 12:        /* Host name */
-               ic_bootp_string(utsname()->nodename, ext+1, *ext,
-                               __NEW_UTS_LEN);
-               ic_host_name_set = 1;
+               if (!ic_host_name_set) {
+                       ic_bootp_string(utsname()->nodename, ext+1, *ext,
+                                       __NEW_UTS_LEN);
+                       ic_host_name_set = 1;
+               }
                break;
        case 15:        /* Domain name (DNS) */
-               ic_bootp_string(ic_domain, ext+1, *ext, sizeof(ic_domain));
+               if (!ic_domain[0])
+                       ic_bootp_string(ic_domain, ext+1, *ext, sizeof(ic_domain));
                break;
        case 17:        /* Root path */
                if (!root_server_path[0])