mdev: support $ENVVAR=regex

1 files changed, 42 insertions, 27 deletions

diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index a3275f881..ea1edcc40 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -89,15 +89,11 @@ static char *build_alias(char *alias, const char *device_name)
 /* NB: "mdev -s" may call us many times, do not leak memory/fds! */
 static void make_device(char *path, int delete)
 {
-        const char *device_name;
+        char *device_name;
         int major, minor, type, len;
         int mode;
-        char *dev_maj_min = path + strlen(path);
         parser_t *parser;
 
-        /* Force the configuration file settings exactly. */
-        umask(0);
-
         /* Try to read major/minor string.  Note that the kernel puts \n after
          * the data, so we don't need to worry about null terminating the string
          * because sscanf() will stop at the first nondigit, which \n is.
@@ -105,21 +101,23 @@ static void make_device(char *path, int delete)
          */
         major = -1;
         if (!delete) {
+                char *dev_maj_min = path + strlen(path);
+
                 strcpy(dev_maj_min, "/dev");
                 len = open_read_close(path, dev_maj_min + 1, 64);
-                *dev_maj_min++ = '\0';
+                *dev_maj_min = '\0';
                 if (len < 1) {
                         if (!ENABLE_FEATURE_MDEV_EXEC)
                                 return;
-                        /* no "dev" file, so just try to run script */
-                        *dev_maj_min = '\0';
-                } else if (sscanf(dev_maj_min, "%u:%u", &major, &minor) != 2) {
+                        /* no "dev" file, but we can still run scripts
+                         * based on device name */
+                } else if (sscanf(++dev_maj_min, "%u:%u", &major, &minor) != 2) {
                         major = -1;
                 }
         }
 
         /* Determine device name, type, major and minor */
-        device_name = bb_basename(path);
+        device_name = (char*) bb_basename(path);
         /* http://kernel.org/doc/pending/hotplug.txt says that only
          * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
          * But since 2.6.25 block devices are also in /sys/class/block,
@@ -139,9 +137,7 @@ static void make_device(char *path, int delete)
                 parser = config_open2("/etc/mdev.conf", fopen_for_read);
 
         do {
-                regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
                 int keep_matching;
-                char *val, *name;
                 struct bb_uidgid_t ugid;
                 char *tokens[4];
                 char *command = NULL;
@@ -156,19 +152,22 @@ static void make_device(char *path, int delete)
                 if (ENABLE_FEATURE_MDEV_CONF
                  && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
                 ) {
+                        char *val;
+                        char *str_to_match;
+                        regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
+
                         val = tokens[0];
                         keep_matching = ('-' == val[0]);
                         val += keep_matching; /* swallow leading dash */
 
                         /* Match against either "subsystem/device_name"
                          * or "device_name" alone */
-                        name = strchr(val, '/') ? path : (char *) device_name;
+                        str_to_match = strchr(val, '/') ? path : device_name;
 
                         /* Fields: regex uid:gid mode [alias] [cmd] */
 
-                        /* 1st field: @<numeric maj,min>... */
                         if (val[0] == '@') {
-                                /* @major,minor[-last] */
+                                /* @major,minor[-minor2] */
                                 /* (useful when name is ambiguous:
                                  * "/sys/class/usb/lp0" and
                                  * "/sys/class/printer/lp0") */
@@ -182,15 +181,29 @@ static void make_device(char *path, int delete)
                                 ) {
                                         continue; /* this line doesn't match */
                                 }
-                        } else { /* ... or regex to match device name */
+                                goto line_matches;
+                        }
+                        if (val[0] == '$') {
+                                /* regex to match an environment variable */
+                                char *eq = strchr(++val, '=');
+                                if (!eq)
+                                        continue;
+                                *eq = '\0';
+                                str_to_match = getenv(val);
+                                if (!str_to_match)
+                                        continue;
+                                str_to_match -= strlen(val) + 1;
+                                *eq = '=';
+                        }
+                        /* else: regex to match [subsystem/]device_name */
+
+                        {
                                 regex_t match;
                                 int result;
 
-                                /* Is this it? */
                                 xregcomp(&match, val, REG_EXTENDED);
-                                result = regexec(&match, name, ARRAY_SIZE(off), off, 0);
+                                result = regexec(&match, str_to_match, ARRAY_SIZE(off), off, 0);
                                 regfree(&match);
-
                                 //bb_error_msg("matches:");
                                 //for (int i = 0; i < ARRAY_SIZE(off); i++) {
                                 //      if (off[i].rm_so < 0) continue;
@@ -199,17 +212,17 @@ static void make_device(char *path, int delete)
                                 //              device_name + off[i].rm_so);
                                 //}
 
-                                /* If not this device, skip rest of line */
+                                /* If no match, skip rest of line */
                                 /* (regexec returns whole pattern as "range" 0) */
                                 if (result || off[0].rm_so
-                                 || ((int)off[0].rm_eo != (int)strlen(name))
+                                 || ((int)off[0].rm_eo != (int)strlen(str_to_match))
                                 ) {
                                         continue; /* this line doesn't match */
                                 }
                         }
-
-                        /* This line matches: stop parsing the file after parsing
-                         * the rest of fields unless keep_matching == 1 */
+ line_matches:
+                        /* This line matches. Stop parsing after parsing
+                         * the rest the line unless keep_matching == 1 */
 
                         /* 2nd field: uid:gid - device ownership */
                         parse_chown_usergroup_or_die(&ugid, tokens[1]);
@@ -243,7 +256,7 @@ static void make_device(char *path, int delete)
                                                         if (*s++ == '%')
                                                                 n++;
 
-                                                p = alias = xzalloc(strlen(a) + n * strlen(name));
+                                                p = alias = xzalloc(strlen(a) + n * strlen(str_to_match));
                                                 s = a + 1;
                                                 while (*s) {
                                                         *p = *s;
@@ -251,7 +264,7 @@ static void make_device(char *path, int delete)
                                                                 i = (s[1] - '0');
                                                                 if (i <= 9 && off[i].rm_so >= 0) {
                                                                         n = off[i].rm_eo - off[i].rm_so;
-                                                                        strncpy(p, name + off[i].rm_so, n);
+                                                                        strncpy(p, str_to_match + off[i].rm_so, n);
                                                                         p += n - 1;
                                                                         s++;
                                                                 }
@@ -447,9 +460,11 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
 
         /* We can be called as hotplug helper */
         /* Kernel cannot provide suitable stdio fds for us, do it ourself */
-
         bb_sanitize_stdio();
 
+        /* Force the configuration file settings exactly */
+        umask(0);
+
         xchdir("/dev");
 
         if (argv[1] && strcmp(argv[1], "-s") == 0) {