lxc-user-nic: fix adding database entries

The code before inserted \0-bytes after every new line which made the db
basically unusable.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/lxc_user_nic.c b/src/lxc/lxc_user_nic.c
index 9164e44dc9fb8dcebbd31f87961c406c7e89566f..39c7daabffad611851b20f402dfc6d5d3de7c4b9 100644 (file)
--- a/src/lxc/lxc_user_nic.c
+++ b/src/lxc/lxc_user_nic.c
@@ -678,7 +678,7 @@ static char *get_nic_if_avail(int fd, struct alloted_s *names, int pid,
                              char *intype, char *br, int allowed, char **cnic)
 {
        int ret;
-       off_t len, slen;
+       size_t slen;
        char *newline, *nicname, *owner;
        struct stat sb;
        struct alloted_s *n;
@@ -693,31 +693,32 @@ static char *get_nic_if_avail(int fd, struct alloted_s *names, int pid,
 
        owner = names->name;
 
-       if (fstat(fd, &sb) < 0) {
+       ret = fstat(fd, &sb);
+       if (ret < 0) {
                usernic_error("Failed to fstat: %s\n", strerror(errno));
                return NULL;
        }
 
-       len = sb.st_size;
-       if (len > 0) {
-               buf =
-                   mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+       if (sb.st_size > 0) {
+               buf = lxc_strmmap(NULL, sb.st_size, PROT_READ | PROT_WRITE,
+                                 MAP_SHARED, fd, 0);
                if (buf == MAP_FAILED) {
-                       usernic_error("Failed to establish shared memory mapping: %s\n",
-                                     strerror(errno));
+                       usernic_error("Failed to establish shared memory "
+                                     "mapping: %s\n", strerror(errno));
                        return NULL;
                }
 
                owner = NULL;
                for (n = names; n != NULL; n = n->next) {
-                       count = count_entries(buf, len, n->name, intype, br);
-
+                       count = count_entries(buf, sb.st_size, n->name, intype, br);
                        if (count >= n->allowed)
                                continue;
 
                        owner = n->name;
                        break;
                }
+
+               lxc_strmunmap(buf, sb.st_size);
        }
 
        if (owner == NULL)
@@ -729,41 +730,67 @@ static char *get_nic_if_avail(int fd, struct alloted_s *names, int pid,
                return NULL;
        }
 
-       /* owner  ' ' intype ' ' br ' ' *nicname + '\n' + '\0' */
-       slen = strlen(owner) + strlen(intype) + strlen(br) + strlen(nicname) + 5;
-       newline = alloca(slen);
+       /* strlen(owner)
+        * +
+        * " "
+        * +
+        * strlen(intype)
+        * +
+        * " "
+        * +
+        * strlen(br)
+        * +
+        * " "
+        * +
+        * strlen(nicname)
+        * +
+        * \n
+        * +
+        * \0
+        */
+       slen = strlen(owner) + strlen(intype) + strlen(br) + strlen(nicname) + 4;
+       newline = malloc(slen + 1);
        if (!newline) {
                free(nicname);
+               free(newline);
                usernic_error("Failed allocate memory: %s\n", strerror(errno));
                return NULL;
        }
 
-       ret = snprintf(newline, slen, "%s %s %s %s\n", owner, intype, br, nicname);
-       if (ret < 0 || ret >= slen) {
+       ret = snprintf(newline, slen + 1, "%s %s %s %s\n", owner, intype, br, nicname);
+       if (ret < 0 || (size_t)ret >= (slen + 1)) {
                if (lxc_netdev_delete_by_name(nicname) != 0)
                        usernic_error("Error unlinking %s\n", nicname);
                free(nicname);
+               free(newline);
                return NULL;
        }
-       if (len)
-               munmap(buf, len);
 
-       if (ftruncate(fd, len + slen))
-               usernic_error("Failed to set new file size: %s\n",
-                             strerror(errno));
+       /* Note that the file needs to be truncated to the size **without** the
+        * \0 byte! Files are not \0-terminated!
+        */
+       ret = ftruncate(fd, sb.st_size + slen);
+       if (ret < 0)
+               usernic_error("Failed to truncate file: %s\n", strerror(errno));
 
-       buf = mmap(NULL, len + slen, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+       buf = lxc_strmmap(NULL, sb.st_size + slen, PROT_READ | PROT_WRITE,
+                         MAP_SHARED, fd, 0);
        if (buf == MAP_FAILED) {
                usernic_error("Failed to establish shared memory mapping: %s\n",
                              strerror(errno));
                if (lxc_netdev_delete_by_name(nicname) != 0)
                        usernic_error("Error unlinking %s\n", nicname);
                free(nicname);
+               free(newline);
                return NULL;
        }
 
-       strcpy(buf + len, newline);
-       munmap(buf, len + slen);
+       /* Note that the memory needs to be moved in the buffer **without** the
+        * \0 byte! Files are not \0-terminated!
+        */
+       memmove(buf + sb.st_size, newline, slen);
+       free(newline);
+       lxc_strmunmap(buf, sb.st_size + slen);
 
        return nicname;
 }