diff options
Diffstat (limited to 'mount.c')
| -rw-r--r-- | mount.c | 144 |
1 files changed, 144 insertions, 0 deletions
@@ -22,8 +22,152 @@ #define _GNU_SOURCE +#include <hurd/fsys.h> +#include <fcntl.h> + #include "mount.h" +#include "lib.h" /* The command line for starting the mountee. */ char * mountee_argz; size_t mountee_argz_len; + +/* The node the mountee is sitting on. */ +node_t * mountee_node; + +mach_port_t mountee_root; + +int mountee_started = 0; + +/* Starts the mountee (given by `argz` and `argz_len`), attaches it to + the node `np` and opens a port `port` to the mountee. */ +error_t +start_mountee (node_t * np, char * argz, size_t argz_len, mach_port_t * port) +{ + error_t err; + mach_port_t underlying_port; + + mach_port_t mountee_control; + + /* Identity information about the unionfs process (for + fsys_getroot). */ + uid_t * uids; + size_t nuids; + + gid_t * gids; + size_t ngids; + + /* The retry information returned by fsys_getroot. */ + string_t retry_name; + mach_port_t retry_port; + + /* Fetch the effective UIDs of the unionfs process. */ + nuids = geteuids (0, 0); + if (nuids < 0) + return EPERM; + uids = alloca (nuids * sizeof (uid_t)); + + nuids = geteuids (nuids, uids); + if (nuids < 0) + return EPERM; + + /* Fetch the effective GIDs of the unionfs process. */ + ngids = getgroups (0, 0); + if (ngids < 0) + return EPERM; + gids = alloca (ngids * sizeof (gid_t)); + + ngids = getgroups (ngids, gids); + if (ngids < 0) + return EPERM; + + /* Opens the port on which to set the mountee. */ + error_t open_port (int flags, mach_port_t * underlying, + mach_msg_type_name_t * underlying_type, task_t task, + void *cookie) + { + err = 0; + + /* The protid which will contain the port to the node on which the + mountee will be sitting. */ + struct protid * newpi; + + struct iouser * unionfs_user; + + /* Initialize `unionfs_user` with the effective UIDs and GIDs of + the unionfs process. */ + err = iohelp_create_complex_iouser (&unionfs_user, uids, nuids, gids, ngids); + if (err) + return err; + + /* Create a port to node on which the mountee should sit (np). */ + newpi = netfs_make_protid + (netfs_make_peropen (np, flags, NULL), unionfs_user); + if (!newpi) + { + iohelp_free_iouser (unionfs_user); + return errno; + } + + *underlying = underlying_port = ports_get_send_right (newpi); + *underlying_type = MACH_MSG_TYPE_COPY_SEND; + + ports_port_deref (newpi); + + return err; + } /*open_port */ + + /* Start the translator. The value 60000 for the timeout is the one + found in settrans. */ + err = fshelp_start_translator (open_port, NULL, argz, argz, argz_len, + 60000, &mountee_control); + if (err) + return err; + + /* Attach the mountee to the port opened in the previous call. */ + err = file_set_translator (underlying_port, 0, FS_TRANS_SET, 0, argz, + argz_len, mountee_control, MACH_MSG_TYPE_COPY_SEND); + port_dealloc (underlying_port); + if (err) + return err; + + /* Obtain the port to the root of the newly-set translator. + + Note that the O_READ flag does not actually limit access to the + mountee's filesystem considerably. Whenever a client looks up a + node which is not a directory, unionfs will give off a port to + the node itself, withouth proxying it. Proxying happens only for + directory nodes. */ + err = fsys_getroot (mountee_control, MACH_PORT_NULL, MACH_MSG_TYPE_COPY_SEND, + uids, nuids, gids, ngids, O_READ, &retry_port, + retry_name, port); + return err; +} /* start_mountee */ + +/* Sets up a proxy node and sets the translator on it. */ +error_t +setup_unionmount (void) +{ + error_t err = 0; + + /* The mountee will be sitting on this node. This node is based on + the netnode of the root node (it is essentially a clone of the + root node), so that unionfs appears as the underlying translator + to the mountee. Note the we cannot set the mountee on the root + node directly, because in this case the mountee's filesystem + would obscure the filesystem published by unionfs. */ + mountee_node = netfs_make_node (netfs_root_node->nn); + if (!mountee_node) + return ENOMEM; + + /* Set the mountee on the new node. */ + err = start_mountee (mountee_node, mountee_argz, mountee_argz_len, + &mountee_root); + if (err) + return err; + + mountee_started = 1; + + return 0; +} /* setup_unionmount */ + |