fs/cifs/cifsroot.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * SMB root file system support
   4  *
   5  * Copyright (c) 2019 Paulo Alcantara <palcantara@suse.de>
   6  */
   7 #include <linux/init.h>
   8 #include <linux/fs.h>
   9 #include <linux/types.h>
  10 #include <linux/ctype.h>
  11 #include <linux/string.h>
  12 #include <linux/root_dev.h>
  13 #include <linux/kernel.h>
  14 #include <linux/in.h>
  15 #include <linux/inet.h>
  16 #include <net/ipconfig.h>
  17
  18 #define DEFAULT_MNT_OPTS \
  19         "vers=1.0,cifsacl,mfsymlinks,rsize=1048576,wsize=65536,uid=0,gid=0," \
  20         "hard,rootfs"
  21
  22 static char root_dev[2048] __initdata = "";
  23 static char root_opts[1024] __initdata = DEFAULT_MNT_OPTS;
  24
  25 static __be32 __init parse_srvaddr(char *start, char *end)
  26 {
  27         /* TODO: ipv6 support */
  28         char addr[sizeof("aaa.bbb.ccc.ddd")];
  29         int i = 0;
  30
  31         while (start < end && i < sizeof(addr) - 1) {
  32                 if (isdigit(*start) || *start == '.')
  33                         addr[i++] = *start;
  34                 start++;
  35         }
  36         addr[i] = '\0';
  37         return in_aton(addr);
  38 }
  39
  40 /* cifsroot=//<server-ip>/<share>[,options] */
  41 static int __init cifs_root_setup(char *line)
  42 {
  43         char *s;
  44         int len;
  45         __be32 srvaddr = htonl(INADDR_NONE);
  46
  47         ROOT_DEV = Root_CIFS;
  48
  49         if (strlen(line) > 3 && line[0] == '/' && line[1] == '/') {
  50                 s = strchr(&line[2], '/');
  51                 if (!s || s[1] == '\0')
  52                         return 1;
  53
  54                 /* make s point to ',' or '\0' at end of line */
  55                 s = strchrnul(s, ',');
  56                 /* len is strlen(unc) + '\0' */
  57                 len = s - line + 1;
  58                 if (len > sizeof(root_dev)) {
  59                         pr_err("Root-CIFS: UNC path too long\n");
  60                         return 1;
  61                 }
  62                 strlcpy(root_dev, line, len);
  63                 srvaddr = parse_srvaddr(&line[2], s);
  64                 if (*s) {
  65                         int n = snprintf(root_opts,
  66                                          sizeof(root_opts), "%s,%s",
  67                                          DEFAULT_MNT_OPTS, s + 1);
  68                         if (n >= sizeof(root_opts)) {
  69                                 pr_err("Root-CIFS: mount options string too long\n");
  70                                 root_opts[sizeof(root_opts)-1] = '\0';
  71                                 return 1;
  72                         }
  73                 }
  74         }
  75
  76         root_server_addr = srvaddr;
  77
  78         return 1;
  79 }
  80
  81 __setup("cifsroot=", cifs_root_setup);
  82
  83 int __init cifs_root_data(char **dev, char **opts)
  84 {
  85         if (!root_dev[0] || root_server_addr == htonl(INADDR_NONE)) {
  86                 pr_err("Root-CIFS: no SMB server address\n");
  87                 return -1;
  88         }
  89
  90         *dev = root_dev;
  91         *opts = root_opts;
  92
  93         return 0;
  94 }