minix/lib/libpuffs/path.c

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/*
* This file contains the procedures that look up path names in the directory
* system and determine the pnode number that goes with a given path name.
*
* Created (based on MFS):
* June 2011 (Evgeniy Ivanov)
*/
#include "fs.h"
#include <sys/cdefs.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <assert.h>
#include <errno.h>
#include <puffs.h>
#include <stdlib.h>
#include <string.h>
#include <minix/endpoint.h>
#include <minix/vfsif.h>
#include <minix/libminixfs.h>
#include "puffs.h"
#include "puffs_priv.h"
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char dot2[3] = ".."; /* permissions for . and .. */
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static char *get_name(char *name, char string[NAME_MAX+1]);
static int ltraverse(struct puffs_node *pn, char *suffix);
static int parse_path(pino_t dir_ino, pino_t root_ino, int flags, struct
puffs_node **res_inop, size_t *offsetp, int *symlinkp);
/*===========================================================================*
* fs_lookup *
*===========================================================================*/
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int fs_lookup()
{
cp_grant_id_t grant;
int r, r1, flags, symlinks;
unsigned int len;
size_t offset = 0, path_size;
pino_t dir_ino, root_ino;
struct puffs_node *pn;
grant = (cp_grant_id_t) fs_m_in.REQ_GRANT;
path_size = (size_t) fs_m_in.REQ_PATH_SIZE; /* Size of the buffer */
len = (int) fs_m_in.REQ_PATH_LEN; /* including terminating nul */
dir_ino = (pino_t) fs_m_in.REQ_DIR_INO;
root_ino = (pino_t) fs_m_in.REQ_ROOT_INO;
flags = (int) fs_m_in.REQ_FLAGS;
/* Check length. */
if (len > sizeof(user_path)) return(E2BIG); /* too big for buffer */
if (len == 0) return(EINVAL); /* too small */
/* Copy the pathname and set up caller's user and group id */
r = sys_safecopyfrom(VFS_PROC_NR, grant, /*offset*/ 0,
(vir_bytes) user_path, (size_t) len);
if (r != OK) return(r);
/* Verify this is a null-terminated path. */
if (user_path[len - 1] != '\0') return(EINVAL);
memset(&credentials, 0, sizeof(credentials));
if(!(flags & PATH_GET_UCRED)) { /* Do we have to copy uid/gid credentials? */
caller_uid = (uid_t) fs_m_in.REQ_UID;
caller_gid = (gid_t) fs_m_in.REQ_GID;
} else {
if((r=fs_lookup_credentials(&credentials,
&caller_uid, &caller_gid,
(cp_grant_id_t) fs_m_in.REQ_GRANT2,
(size_t) fs_m_in.REQ_UCRED_SIZE)) != OK)
return r;
}
/* Lookup pnode */
pn = NULL;
r = parse_path(dir_ino, root_ino, flags, &pn, &offset, &symlinks);
if (symlinks != 0 && (r == ELEAVEMOUNT || r == EENTERMOUNT || r == ESYMLINK)){
len = strlen(user_path)+1;
if (len > path_size) return(ENAMETOOLONG);
r1 = sys_safecopyto(VFS_PROC_NR, grant, (vir_bytes) 0,
(vir_bytes) user_path, (size_t) len);
if (r1 != OK) return(r1);
}
if (r == ELEAVEMOUNT || r == ESYMLINK) {
/* Report offset and the error */
fs_m_out.RES_OFFSET = offset;
fs_m_out.RES_SYMLOOP = symlinks;
return(r);
}
if (r != OK && r != EENTERMOUNT) {
return(r);
}
if (r == OK) {
/* Open pnode */
pn->pn_count++;
}
fs_m_out.RES_INODE_NR = pn->pn_va.va_fileid;
fs_m_out.RES_MODE = pn->pn_va.va_mode;
fs_m_out.RES_FILE_SIZE_LO = pn->pn_va.va_size;
fs_m_out.RES_SYMLOOP = symlinks;
fs_m_out.RES_UID = pn->pn_va.va_uid;
fs_m_out.RES_GID = pn->pn_va.va_gid;
/* This is only valid for block and character specials. But it doesn't
* cause any harm to set RES_DEV always. */
fs_m_out.RES_DEV = pn->pn_va.va_rdev;
if (r == EENTERMOUNT) {
fs_m_out.RES_OFFSET = offset;
}
return(r);
}
/*===========================================================================*
* parse_path *
*===========================================================================*/
static int parse_path(
pino_t dir_ino,
pino_t root_ino,
int flags,
struct puffs_node **res_inop,
size_t *offsetp,
int *symlinkp
) {
/* Parse the path in user_path, starting at dir_ino. If the path is the empty
* string, just return dir_ino. It is upto the caller to treat an empty
* path in a special way. Otherwise, if the path consists of just one or
* more slash ('/') characters, the path is replaced with ".". Otherwise,
* just look up the first (or only) component in path after skipping any
* leading slashes.
*/
int r, leaving_mount;
struct puffs_node *pn, *pn_dir;
char *cp, *next_cp; /* component and next component */
char component[NAME_MAX+1];
/* Start parsing path at the first component in user_path */
cp = user_path;
/* No symlinks encountered yet */
*symlinkp = 0;
/* Find starting pnode according to the request message */
/* XXX it's deffinitely OK to use nodewalk here */
if ((pn = puffs_pn_nodewalk(global_pu, 0, &dir_ino)) == NULL) {
lpuffs_debug("nodewalk failed\n");
return(ENOENT);
}
/* If dir has been removed return ENOENT. */
if (pn->pn_va.va_nlink == NO_LINK) return(ENOENT);
/* If the given start pnode is a mountpoint, we must be here because the file
* system mounted on top returned an ELEAVEMOUNT error. In this case, we must
* only accept ".." as the first path component.
*/
leaving_mount = pn->pn_mountpoint; /* True iff pn is a mountpoint */
/* Scan the path component by component. */
while (TRUE) {
if (cp[0] == '\0') {
/* We're done; either the path was empty or we've parsed all
components of the path */
*res_inop = pn;
*offsetp += cp - user_path;
/* Return EENTERMOUNT if we are at a mount point */
if (pn->pn_mountpoint) return(EENTERMOUNT);
return(OK);
}
while(cp[0] == '/') cp++;
next_cp = get_name(cp, component);
if (next_cp == NULL) {
return(err_code);
}
/* Special code for '..'. A process is not allowed to leave a chrooted
* environment. A lookup of '..' at the root of a mounted filesystem
* has to return ELEAVEMOUNT. In both cases, the caller needs search
* permission for the current pnode, as it is used as directory.
*/
if (strcmp(component, "..") == 0) {
/* 'pn' is now accessed as directory */
if ((r = forbidden(pn, X_BIT)) != OK) {
return(r);
}
if (pn->pn_va.va_fileid == root_ino) {
cp = next_cp;
continue; /* Ignore the '..' at a process' root
and move on to the next component */
}
if (pn->pn_va.va_fileid == global_pu->pu_pn_root->pn_va.va_fileid
&& !is_root_fs) {
/* Climbing up to parent FS */
*offsetp += cp - user_path;
return(ELEAVEMOUNT);
}
}
/* Only check for a mount point if we are not coming from one. */
if (!leaving_mount && pn->pn_mountpoint) {
/* Going to enter a child FS */
*res_inop = pn;
*offsetp += cp - user_path;
return(EENTERMOUNT);
}
/* There is more path. Keep parsing.
* If we're leaving a mountpoint, skip directory permission checks.
*/
pn_dir = pn;
if ((pn_dir->pn_va.va_mode & I_TYPE) != I_DIRECTORY) {
return(ENOTDIR);
}
pn = advance(pn_dir, leaving_mount ? dot2 : component, CHK_PERM);
if (err_code == ELEAVEMOUNT || err_code == EENTERMOUNT)
err_code = OK;
if (err_code != OK) {
return(err_code);
}
assert(pn != NULL);
leaving_mount = 0;
/* The call to advance() succeeded. Fetch next component. */
if (S_ISLNK(pn->pn_va.va_mode)) {
if (next_cp[0] == '\0' && (flags & PATH_RET_SYMLINK)) {
*res_inop = pn;
*offsetp += next_cp - user_path;
return(OK);
}
/* Extract path name from the symlink file */
r = ltraverse(pn, next_cp);
next_cp = user_path;
*offsetp = 0;
/* Symloop limit reached? */
if (++(*symlinkp) > _POSIX_SYMLOOP_MAX)
r = ELOOP;
if (r != OK)
return(r);
if (next_cp[0] == '/')
return(ESYMLINK);
pn = pn_dir;
}
cp = next_cp; /* Process subsequent component in next round */
}
}
/*===========================================================================*
* ltraverse *
*===========================================================================*/
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static int ltraverse(pn, suffix)
register struct puffs_node *pn;/* symbolic link */
char *suffix; /* current remaining path. Has to point in the
* user_path buffer
*/
{
/* Traverse a symbolic link. Copy the link text from the pnode and insert
* the text into the path. Return error code or report success. Base
* directory has to be determined according to the first character of the
* new pathname.
*/
int r;
char sp[PATH_MAX];
size_t llen = PATH_MAX;/* length of link */
size_t slen; /* length of suffix */
PUFFS_MAKECRED(pcr, &global_kcred);
if (!S_ISLNK(pn->pn_va.va_mode))
r = EACCES;
if (global_pu->pu_ops.puffs_node_readlink == NULL)
return(EINVAL);
if (global_pu->pu_ops.puffs_node_readlink(global_pu, pn, pcr, sp, &llen) != 0)
return(EINVAL);
slen = strlen(suffix);
/* The path we're parsing looks like this:
* /already/processed/path/<link> or
* /already/processed/path/<link>/not/yet/processed/path
* After expanding the <link>, the path will look like
* <expandedlink> or
* <expandedlink>/not/yet/processed
* In both cases user_path must have enough room to hold <expandedlink>.
* However, in the latter case we have to move /not/yet/processed to the
* right place first, before we expand <link>. When strlen(<expandedlink>) is
* smaller than strlen(/already/processes/path), we move the suffix to the
* left. Is strlen(<expandedlink>) greater then we move it to the right. Else
* we do nothing.
*/
if (slen > 0) { /* Do we have path after the link? */
/* For simplicity we require that suffix starts with a slash */
if (suffix[0] != '/') {
panic("ltraverse: suffix does not start with a slash");
}
/* To be able to expand the <link>, we have to move the 'suffix'
* to the right place.
*/
if (slen + llen + 1 > sizeof(user_path))
return(ENAMETOOLONG);/* <expandedlink>+suffix+\0 does not fit*/
if ((unsigned)(suffix - user_path) != llen) {
/* Move suffix left or right if needed */
memmove(&user_path[llen], suffix, slen+1);
}
} else {
if (llen + 1 > sizeof(user_path))
return(ENAMETOOLONG); /* <expandedlink> + \0 does not fit */
/* Set terminating nul */
user_path[llen]= '\0';
}
/* Everything is set, now copy the expanded link to user_path */
memmove(user_path, sp, llen);
return(OK);
}
/*===========================================================================*
* advance *
*===========================================================================*/
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struct puffs_node *advance(pn_dir, string, chk_perm)
struct puffs_node *pn_dir; /* pnode for directory to be searched */
char string[NAME_MAX + 1]; /* component name to look for */
int chk_perm; /* check permissions when string is looked up*/
{
/* Given a directory and a component of a path, look up the component in
* the directory, find the pnode, open it, and return a pointer to its pnode
* slot.
* TODO: instead of string, should get pcn.
*/
struct puffs_node *pn;
struct puffs_newinfo pni;
struct puffs_kcn pkcnp;
PUFFS_MAKECRED(pcr, &global_kcred);
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struct puffs_cn pcn = {&pkcnp, (struct puffs_cred *) __UNCONST(pcr), {0,0,0}};
enum vtype node_vtype;
voff_t size;
dev_t rdev;
int error;
err_code = OK;
/* If 'string' is empty, return an error. */
if (string[0] == '\0') {
err_code = ENOENT;
return(NULL);
}
/* Check for NULL. */
if (pn_dir == NULL)
return(NULL);
if (chk_perm) {
/* Just search permission is checked */
if (forbidden(pn_dir, X_BIT)) {
err_code = EACCES;
return(NULL);
}
}
if (strcmp(string, ".") == 0) {
/* Otherwise we will fall into trouble: path for pnode to be looked up
* will be parent path (same pnode as the one to be looked up) +
* requested path. E.g. after several lookups we might get advance
* for "." with parent path "/././././././././.".
*
* Another problem is that after lookup pnode will be added
* to the pu_pnodelst, which already contains pnode instance for this
* pnode. It will cause lot of troubles.
*/
return pn_dir;
}
pni.pni_cookie = (void** )&pn;
pni.pni_vtype = &node_vtype;
pni.pni_size = &size;
pni.pni_rdev = &rdev;
pcn.pcn_namelen = strlen(string);
assert(pcn.pcn_namelen <= MAXPATHLEN);
strcpy(pcn.pcn_name, string);
if (buildpath) {
if (puffs_path_pcnbuild(global_pu, &pcn, pn_dir) != 0) {
lpuffs_debug("pathbuild error\n");
err_code = ENOENT;
return(NULL);
}
}
/* lookup *must* be present */
error = global_pu->pu_ops.puffs_node_lookup(global_pu, pn_dir,
&pni, &pcn);
if (buildpath) {
if (error) {
global_pu->pu_pathfree(global_pu, &pcn.pcn_po_full);
err_code = ENOENT;
return(NULL);
} else {
struct puffs_node *_pn;
/*
* did we get a new node or a
* recycled node?
*/
_pn = PU_CMAP(global_pu, pn);
if (_pn->pn_po.po_path == NULL)
_pn->pn_po = pcn.pcn_po_full;
else
global_pu->pu_pathfree(global_pu, &pcn.pcn_po_full);
}
}
if (error) {
err_code = error < 0 ? error : -error;
return(NULL);
} else {
/* In MFS/ext2 it's set by search_dir, puffs_node_lookup error codes are unclear,
* so we use error variable there
*/
err_code = OK;
}
assert(pn != NULL);
/* The following test is for "mountpoint/.." where mountpoint is a
* mountpoint. ".." will refer to the root of the mounted filesystem,
* but has to become a reference to the parent of the 'mountpoint'
* directory.
*
* This case is recognized by the looked up name pointing to a
* root pnode, and the directory in which it is held being a
* root pnode, _and_ the name[1] being '.'. (This is a test for '..'
* and excludes '.'.)
*/
if (pn->pn_va.va_fileid == global_pu->pu_pn_root->pn_va.va_fileid) {
if (pn_dir->pn_va.va_fileid == global_pu->pu_pn_root->pn_va.va_fileid) {
if (string[1] == '.') {
if (!is_root_fs) {
/* Climbing up mountpoint */
err_code = ELEAVEMOUNT;
}
}
}
}
/* See if the pnode is mounted on. If so, switch to root directory of the
* mounted file system. The super_block provides the linkage between the
* pnode mounted on and the root directory of the mounted file system.
*/
if (pn->pn_mountpoint) {
/* Mountpoint encountered, report it */
err_code = EENTERMOUNT;
}
return(pn);
}
/*===========================================================================*
* get_name *
*===========================================================================*/
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static char *get_name(path_name, string)
char *path_name; /* path name to parse */
char string[NAME_MAX+1]; /* component extracted from 'old_name' */
{
/* Given a pointer to a path name in fs space, 'path_name', copy the first
* component to 'string' (truncated if necessary, always nul terminated).
* A pointer to the string after the first component of the name as yet
* unparsed is returned. Roughly speaking,
* 'get_name' = 'path_name' - 'string'.
*
* This routine follows the standard convention that /usr/ast, /usr//ast,
* //usr///ast and /usr/ast/ are all equivalent.
*
* If len of component is greater, than allowed, then return 0.
*/
size_t len;
char *cp, *ep;
cp = path_name;
/* Skip leading slashes */
while (cp[0] == '/') cp++;
/* Find the end of the first component */
ep = cp;
while (ep[0] != '\0' && ep[0] != '/')
ep++;
len = (size_t) (ep - cp);
/* XXX we don't check name_max of fileserver (probably we can't) */
if (len > NAME_MAX) {
err_code = ENAMETOOLONG;
return(NULL);
}
/* Special case of the string at cp is empty */
if (len == 0)
strcpy(string, "."); /* Return "." */
else {
memcpy(string, cp, len);
string[len]= '\0';
}
return(ep);
}