minix/servers/vfs/link.c
Thomas Veerman 13ef7f1f38 Prepare VFS to support back calls from PFS. For security reasons and to support
file descriptor passing, PFS does some back calls to VFS. For example, to
verify the validity of a path provided by a process and to tell VFS it must
copy file descriptors from one process to another.
2010-08-30 13:44:07 +00:00

328 lines
9.7 KiB
C

/* This file handles the LINK and UNLINK system calls. It also deals with
* deallocating the storage used by a file when the last UNLINK is done to a
* file and the blocks must be returned to the free block pool.
*
* The entry points into this file are
* do_link: perform the LINK system call
* do_unlink: perform the UNLINK and RMDIR system calls
* do_rename: perform the RENAME system call
* do_truncate: perform the TRUNCATE system call
* do_ftruncate: perform the FTRUNCATE system call
* do_rdlink: perform the RDLNK system call
*/
#include "fs.h"
#include <sys/stat.h>
#include <string.h>
#include <minix/com.h>
#include <minix/callnr.h>
#include <dirent.h>
#include "file.h"
#include "fproc.h"
#include "param.h"
#include <minix/vfsif.h>
#include "vnode.h"
/*===========================================================================*
* do_link *
*===========================================================================*/
PUBLIC int do_link()
{
/* Perform the link(name1, name2) system call. */
int r = OK;
struct vnode *vp, *vp_d;
/* See if 'name1' (file to be linked to) exists. */
if(fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
if ((vp = eat_path(PATH_NOFLAGS, fp)) == NULL) return(err_code);
/* Does the final directory of 'name2' exist? */
if (fetch_name(m_in.name2, m_in.name2_length, M1) != OK)
r = err_code;
else if ((vp_d = last_dir(fp)) == NULL)
r = err_code;
if (r != OK) {
put_vnode(vp);
return(r);
}
/* Check for links across devices. */
if(vp->v_fs_e != vp_d->v_fs_e)
r = EXDEV;
else
r = forbidden(vp_d, W_BIT | X_BIT);
if (r == OK)
r = req_link(vp->v_fs_e, vp_d->v_inode_nr, user_fullpath,
vp->v_inode_nr);
put_vnode(vp);
put_vnode(vp_d);
return(r);
}
/*===========================================================================*
* do_unlink *
*===========================================================================*/
PUBLIC int do_unlink()
{
/* Perform the unlink(name) or rmdir(name) system call. The code for these two
* is almost the same. They differ only in some condition testing. Unlink()
* may be used by the superuser to do dangerous things; rmdir() may not.
*/
struct vnode *vldirp, *vp;
int r;
/* Get the last directory in the path. */
if(fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
if ((vldirp = last_dir(fp)) == NULL) return(err_code);
/* Make sure that the object is a directory */
if((vldirp->v_mode & I_TYPE) != I_DIRECTORY) {
put_vnode(vldirp);
return(ENOTDIR);
}
/* The caller must have both search and execute permission */
if ((r = forbidden(vldirp, X_BIT | W_BIT)) != OK) {
put_vnode(vldirp);
return(r);
}
/* Also, if the sticky bit is set, only the owner of the file or a privileged
user is allowed to unlink */
if ((vldirp->v_mode & S_ISVTX) == S_ISVTX) {
/* Look up inode of file to unlink to retrieve owner */
vp = advance(vldirp, PATH_RET_SYMLINK, fp);
if (vp != NULL) {
if(vp->v_uid != fp->fp_effuid && fp->fp_effuid != SU_UID)
r = EPERM;
put_vnode(vp);
} else
r = err_code;
if (r != OK) {
put_vnode(vldirp);
return(r);
}
}
if(call_nr == UNLINK)
r = req_unlink(vldirp->v_fs_e, vldirp->v_inode_nr, user_fullpath);
else
r = req_rmdir(vldirp->v_fs_e, vldirp->v_inode_nr, user_fullpath);
put_vnode(vldirp);
return(r);
}
/*===========================================================================*
* do_rename *
*===========================================================================*/
PUBLIC int do_rename()
{
/* Perform the rename(name1, name2) system call. */
int r = OK, r1;
struct vnode *old_dirp, *new_dirp, *vp;
char old_name[PATH_MAX+1];
/* See if 'name1' (existing file) exists. Get dir and file inodes. */
if(fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
if ((old_dirp = last_dir(fp)) == NULL) return(err_code);
/* If the sticky bit is set, only the owner of the file or a privileged
user is allowed to rename */
if((old_dirp->v_mode & S_ISVTX) == S_ISVTX) {
/* Look up inode of file to unlink to retrieve owner */
vp = advance(old_dirp, PATH_RET_SYMLINK, fp);
if (vp != NULL) {
if(vp->v_uid != fp->fp_effuid && fp->fp_effuid != SU_UID)
r = EPERM;
put_vnode(vp);
} else
r = err_code;
if (r != OK) {
put_vnode(old_dirp);
return(r);
}
}
/* Save the last component of the old name */
if(strlen(user_fullpath) >= sizeof(old_name)) {
put_vnode(old_dirp);
return(ENAMETOOLONG);
}
strcpy(old_name, user_fullpath);
/* See if 'name2' (new name) exists. Get dir inode */
if(fetch_name(m_in.name2, m_in.name2_length, M1) != OK)
r = err_code;
else if ((new_dirp = last_dir(fp)) == NULL)
r = err_code;
if (r != OK) {
put_vnode(old_dirp);
return r;
}
/* Both parent directories must be on the same device. */
if(old_dirp->v_fs_e != new_dirp->v_fs_e) r = EXDEV;
/* Parent dirs must be writable, searchable and on a writable device */
if ((r1 = forbidden(old_dirp, W_BIT|X_BIT)) != OK ||
(r1 = forbidden(new_dirp, W_BIT|X_BIT)) != OK) r = r1;
if(r == OK)
r = req_rename(old_dirp->v_fs_e, old_dirp->v_inode_nr, old_name,
new_dirp->v_inode_nr, user_fullpath);
put_vnode(old_dirp);
put_vnode(new_dirp);
return(r);
}
/*===========================================================================*
* do_truncate *
*===========================================================================*/
PUBLIC int do_truncate()
{
/* truncate_vnode() does the actual work of do_truncate() and do_ftruncate().
* do_truncate() and do_ftruncate() have to get hold of the inode, either
* by name or fd, do checks on it, and call truncate_inode() to do the
* work.
*/
struct vnode *vp;
int r;
if ((off_t) m_in.flength < 0) return(EINVAL);
/* Temporarily open file */
if (fetch_name(m_in.m2_p1, m_in.m2_i1, M1) != OK) return(err_code);
if ((vp = eat_path(PATH_NOFLAGS, fp)) == NULL) return(err_code);
/* Ask FS to truncate the file */
if ((r = forbidden(vp, W_BIT)) == OK)
r = truncate_vnode(vp, m_in.flength);
put_vnode(vp);
return(r);
}
/*===========================================================================*
* do_ftruncate *
*===========================================================================*/
PUBLIC int do_ftruncate()
{
/* As with do_truncate(), truncate_vnode() does the actual work. */
struct filp *rfilp;
if ((off_t) m_in.flength < 0) return(EINVAL);
/* File is already opened; get a vnode pointer from filp */
if ((rfilp = get_filp(m_in.m2_i1)) == NULL) return(err_code);
if (!(rfilp->filp_mode & W_BIT)) return(EBADF);
return truncate_vnode(rfilp->filp_vno, m_in.flength);
}
/*===========================================================================*
* truncate_vnode *
*===========================================================================*/
PUBLIC int truncate_vnode(vp, newsize)
struct vnode *vp;
off_t newsize;
{
int r, file_type;
file_type = vp->v_mode & I_TYPE;
if (file_type != I_REGULAR && file_type != I_NAMED_PIPE) return(EINVAL);
if ((r = req_ftrunc(vp->v_fs_e, vp->v_inode_nr, newsize, 0)) == OK)
vp->v_size = newsize;
return(r);
}
/*===========================================================================*
* do_slink *
*===========================================================================*/
PUBLIC int do_slink()
{
/* Perform the symlink(name1, name2) system call. */
int r;
struct vnode *vp;
if(m_in.name1_length <= 1) return(ENOENT);
if(m_in.name1_length >= SYMLINK_MAX) return(ENAMETOOLONG);
/* Get dir inode of 'name2' */
if(fetch_name(m_in.name2, m_in.name2_length, M1) != OK) return(err_code);
if ((vp = last_dir(fp)) == NULL) return(err_code);
if ((r = forbidden(vp, W_BIT|X_BIT)) == OK) {
r = req_slink(vp->v_fs_e, vp->v_inode_nr, user_fullpath, who_e,
m_in.name1, m_in.name1_length - 1, fp->fp_effuid,
fp->fp_effgid);
}
put_vnode(vp);
return(r);
}
/*===========================================================================*
* rdlink_direct *
*===========================================================================*/
PUBLIC int rdlink_direct(orig_path, link_path, rfp)
char *orig_path;
char *link_path; /* should have length PATH_MAX+1 */
struct fproc *rfp;
{
/* Perform a readlink()-like call from within the VFS */
int r;
struct vnode *vp;
/* Temporarily open the file containing the symbolic link */
strncpy(user_fullpath, orig_path, PATH_MAX);
if ((vp = eat_path(PATH_RET_SYMLINK, rfp)) == NULL) return(err_code);
/* Make sure this is a symbolic link */
if((vp->v_mode & I_TYPE) != I_SYMBOLIC_LINK)
r = EINVAL;
else
r = req_rdlink(vp->v_fs_e, vp->v_inode_nr, (endpoint_t) 0,
link_path, PATH_MAX+1, 1);
put_vnode(vp);
return r;
}
/*===========================================================================*
* do_rdlink *
*===========================================================================*/
PUBLIC int do_rdlink()
{
/* Perform the readlink(name, buf, bufsize) system call. */
int r, copylen;
struct vnode *vp;
copylen = m_in.nbytes;
if(copylen < 0) return(EINVAL);
/* Temporarily open the file containing the symbolic link */
if(fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
if ((vp = eat_path(PATH_RET_SYMLINK, fp)) == NULL) return(err_code);
/* Make sure this is a symbolic link */
if((vp->v_mode & I_TYPE) != I_SYMBOLIC_LINK)
r = EINVAL;
else
r = req_rdlink(vp->v_fs_e, vp->v_inode_nr, who_e, m_in.name2,
copylen, 0);
put_vnode(vp);
return(r);
}