minix/servers/vfs/link.c

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/* 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;
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endpoint_t linked_fs_e, link_lastdir_fs_e;
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)) == NIL_VNODE) 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()) == NIL_VNODE)
r = err_code;
if (r != OK) {
put_vnode(vp);
return(r);
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}
/* 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);
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put_vnode(vp);
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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.
*/
register struct fproc *rfp;
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()) == NIL_VNODE) return(err_code);
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/* Make sure that the object is a directory */
if((vldirp->v_mode & I_TYPE) != I_DIRECTORY) {
put_vnode(vldirp);
return(ENOTDIR);
}
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/* The caller must have both search and execute permission */
if ((r = forbidden(vldirp, X_BIT | W_BIT)) != OK) {
put_vnode(vldirp);
return(r);
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}
/* 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);
if (vp != NIL_VNODE) {
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;
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size_t len;
struct vnode *old_dirp, *new_dirp, *vp;
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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()) == NIL_VNODE) 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);
if (vp != NIL_VNODE) {
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);
}
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}
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/* Save the last component of the old name */
if(strlen(user_fullpath) >= sizeof(old_name)) {
put_vnode(old_dirp);
return(ENAMETOOLONG);
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}
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()) == NIL_VNODE)
r = err_code;
if (r != OK) {
put_vnode(old_dirp);
return r;
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}
/* Both parent directories must be on the same device. */
if(old_dirp->v_fs_e != new_dirp->v_fs_e) r = EXDEV;
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/* 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;
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/* 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)) == NIL_VNODE) return(err_code);
/* Ask FS to truncate the file */
if ((r = forbidden(vp, W_BIT)) == OK)
r = truncate_vnode(vp, m_in.flength);
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put_vnode(vp);
return(r);
}
/*===========================================================================*
* do_ftruncate *
*===========================================================================*/
PUBLIC int do_ftruncate()
{
/* As with do_truncate(), truncate_vnode() does the actual work. */
int r;
struct filp *rfilp;
/* File is already opened; get a vnode pointer from filp */
if ((rfilp = get_filp(m_in.m2_i1)) == NIL_FILP) return(err_code);
if (!(rfilp->filp_mode & W_BIT)) return(EBADF);
return truncate_vnode(rfilp->filp_vno, m_in.m2_l1);
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}
/*===========================================================================*
* truncate_vnode *
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*===========================================================================*/
PUBLIC int truncate_vnode(vp, newsize)
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struct vnode *vp;
off_t newsize;
{
int r, file_type;
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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, linklen;
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struct vnode *vp;
char string[NAME_MAX]; /* last component of the new dir's path name */
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()) == NIL_VNODE) 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);
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}
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put_vnode(vp);
return(r);
}
/*===========================================================================*
* do_rdlink *
*===========================================================================*/
PUBLIC int do_rdlink()
{
/* Perform the readlink(name, buf, bufsize) system call. */
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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)) == NIL_VNODE) 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);
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put_vnode(vp);
return(r);
}