| /* |
| * linux/fs/namei.c |
| * |
| * (C) 1991 Linus Torvalds |
| */ |
| |
| /* |
| * Some corrections by tytso. |
| */ |
| |
| #include <errno.h> |
| #include <const.h> |
| |
| #include <asm/segment.h> |
| |
| #include <linux/sched.h> |
| #include <linux/kernel.h> |
| #include <linux/string.h> |
| #include <linux/fcntl.h> |
| #include <linux/stat.h> |
| |
| struct inode * _namei(const char * filename, struct inode * base, |
| int follow_links); |
| |
| #define ACC_MODE(x) ("\004\002\006\377"[(x)&O_ACCMODE]) |
| |
| /* |
| * comment out this line if you want names > MINIX_NAME_LEN chars to be |
| * truncated. Else they will be disallowed. |
| */ |
| /* #define NO_TRUNCATE */ |
| |
| /* |
| * permission() |
| * |
| * is used to check for read/write/execute permissions on a file. |
| * I don't know if we should look at just the euid or both euid and |
| * uid, but that should be easily changed. |
| */ |
| int permission(struct inode * inode,int mask) |
| { |
| int mode = inode->i_mode; |
| |
| /* special case: not even root can read/write a deleted file */ |
| if (inode->i_dev && !inode->i_nlink) |
| return 0; |
| else if (current->euid == inode->i_uid) |
| mode >>= 6; |
| else if (in_group_p(inode->i_gid)) |
| mode >>= 3; |
| if (((mode & mask & 0007) == mask) || suser()) |
| return 1; |
| return 0; |
| } |
| |
| /* |
| * lookup() looks up one part of a pathname, using the fs-dependent |
| * routines (currently minix_lookup) for it. It also checks for |
| * fathers (pseudo-roots, mount-points) |
| */ |
| int lookup(struct inode * dir,const char * name, int len, |
| struct inode ** result) |
| { |
| struct super_block * sb; |
| |
| *result = NULL; |
| if (len==2 && get_fs_byte(name)=='.' && get_fs_byte(name+1)=='.') { |
| if (dir == current->root) |
| len = 1; |
| else if ((sb = dir->i_sb) && (dir == sb->s_mounted)) { |
| sb = dir->i_sb; |
| iput(dir); |
| if (dir = sb->s_covered) |
| dir->i_count++; |
| } |
| } |
| if (!dir) |
| return -ENOENT; |
| if (!permission(dir,MAY_EXEC)) { |
| iput(dir); |
| return -EACCES; |
| } |
| if (!len) { |
| *result = dir; |
| return 0; |
| } |
| if (!dir->i_op || !dir->i_op->lookup) { |
| iput(dir); |
| return -ENOENT; |
| } |
| return dir->i_op->lookup(dir,name,len,result); |
| } |
| |
| struct inode * follow_link(struct inode * dir, struct inode * inode) |
| { |
| if (!dir || !inode) { |
| iput(dir); |
| iput(inode); |
| return NULL; |
| } |
| if (!inode->i_op || !inode->i_op->follow_link) { |
| iput(dir); |
| return inode; |
| } |
| return inode->i_op->follow_link(dir,inode); |
| } |
| |
| /* |
| * dir_namei() |
| * |
| * dir_namei() returns the inode of the directory of the |
| * specified name, and the name within that directory. |
| */ |
| static struct inode * dir_namei(const char * pathname, |
| int * namelen, const char ** name, struct inode * base) |
| { |
| char c; |
| const char * thisname; |
| int len,error; |
| struct inode * inode; |
| |
| if (!base) { |
| base = current->pwd; |
| base->i_count++; |
| } |
| if ((c=get_fs_byte(pathname))=='/') { |
| iput(base); |
| base = current->root; |
| pathname++; |
| base->i_count++; |
| } |
| while (1) { |
| thisname = pathname; |
| for(len=0;(c=get_fs_byte(pathname++))&&(c!='/');len++) |
| /* nothing */ ; |
| if (!c) |
| break; |
| base->i_count++; |
| error = lookup(base,thisname,len,&inode); |
| if (error) { |
| iput(base); |
| return NULL; |
| } |
| if (!(base = follow_link(base,inode))) |
| return NULL; |
| } |
| *name = thisname; |
| *namelen = len; |
| return base; |
| } |
| |
| struct inode * _namei(const char * pathname, struct inode * base, |
| int follow_links) |
| { |
| const char * basename; |
| int namelen,error; |
| struct inode * inode; |
| |
| if (!(base = dir_namei(pathname,&namelen,&basename,base))) |
| return NULL; |
| base->i_count++; /* lookup uses up base */ |
| error = lookup(base,basename,namelen,&inode); |
| if (error) { |
| iput(base); |
| return NULL; |
| } |
| if (follow_links) |
| inode = follow_link(base,inode); |
| else |
| iput(base); |
| return inode; |
| } |
| |
| struct inode * lnamei(const char * pathname) |
| { |
| return _namei(pathname, NULL, 0); |
| } |
| |
| /* |
| * namei() |
| * |
| * is used by most simple commands to get the inode of a specified name. |
| * Open, link etc use their own routines, but this is enough for things |
| * like 'chmod' etc. |
| */ |
| struct inode * namei(const char * pathname) |
| { |
| return _namei(pathname,NULL,1); |
| } |
| |
| /* |
| * open_namei() |
| * |
| * namei for open - this is in fact almost the whole open-routine. |
| */ |
| int open_namei(const char * pathname, int flag, int mode, |
| struct inode ** res_inode) |
| { |
| const char * basename; |
| int namelen,error; |
| struct inode * dir, *inode; |
| |
| if ((flag & O_TRUNC) && !(flag & O_ACCMODE)) |
| flag |= O_WRONLY; |
| mode &= 07777 & ~current->umask; |
| mode |= I_REGULAR; |
| if (!(dir = dir_namei(pathname,&namelen,&basename,NULL))) |
| return -ENOENT; |
| if (!namelen) { /* special case: '/usr/' etc */ |
| if (!(flag & (O_ACCMODE|O_CREAT|O_TRUNC))) { |
| *res_inode=dir; |
| return 0; |
| } |
| iput(dir); |
| return -EISDIR; |
| } |
| dir->i_count++; /* lookup eats the dir */ |
| error = lookup(dir,basename,namelen,&inode); |
| if (error) { |
| if (!(flag & O_CREAT)) { |
| iput(dir); |
| return error; |
| } |
| if (!permission(dir,MAY_WRITE)) { |
| iput(dir); |
| return -EACCES; |
| } |
| if (!dir->i_op || !dir->i_op->create) { |
| iput(dir); |
| return -EACCES; |
| } |
| return dir->i_op->create(dir,basename,namelen,mode,res_inode); |
| } |
| if (flag & O_EXCL) { |
| iput(dir); |
| iput(inode); |
| return -EEXIST; |
| } |
| if (!(inode = follow_link(dir,inode))) |
| return -ELOOP; |
| if ((S_ISDIR(inode->i_mode) && (flag & O_ACCMODE)) || |
| !permission(inode,ACC_MODE(flag))) { |
| iput(inode); |
| return -EPERM; |
| } |
| inode->i_atime = CURRENT_TIME; |
| if (flag & O_TRUNC) |
| if (inode->i_op && inode->i_op->truncate) { |
| inode->i_size = 0; |
| inode->i_op->truncate(inode); |
| } |
| *res_inode = inode; |
| return 0; |
| } |
| |
| int do_mknod(const char * filename, int mode, int dev) |
| { |
| const char * basename; |
| int namelen; |
| struct inode * dir; |
| |
| if (!(dir = dir_namei(filename,&namelen,&basename, NULL))) |
| return -ENOENT; |
| if (!namelen) { |
| iput(dir); |
| return -ENOENT; |
| } |
| if (!permission(dir,MAY_WRITE)) { |
| iput(dir); |
| return -EACCES; |
| } |
| if (!dir->i_op || !dir->i_op->mknod) { |
| iput(dir); |
| return -EPERM; |
| } |
| return dir->i_op->mknod(dir,basename,namelen,mode,dev); |
| } |
| |
| int sys_mknod(const char * filename, int mode, int dev) |
| { |
| if (S_ISFIFO(mode) || suser()) |
| return do_mknod(filename,mode,dev); |
| return -EPERM; |
| } |
| |
| int sys_mkdir(const char * pathname, int mode) |
| { |
| const char * basename; |
| int namelen; |
| struct inode * dir; |
| |
| if (!(dir = dir_namei(pathname,&namelen,&basename, NULL))) |
| return -ENOENT; |
| if (!namelen) { |
| iput(dir); |
| return -ENOENT; |
| } |
| if (!permission(dir,MAY_WRITE)) { |
| iput(dir); |
| return -EACCES; |
| } |
| if (!dir->i_op || !dir->i_op->mkdir) { |
| iput(dir); |
| return -EPERM; |
| } |
| return dir->i_op->mkdir(dir,basename,namelen,mode); |
| } |
| |
| int sys_rmdir(const char * name) |
| { |
| const char * basename; |
| int namelen; |
| struct inode * dir; |
| |
| if (!(dir = dir_namei(name,&namelen,&basename, NULL))) |
| return -ENOENT; |
| if (!namelen) { |
| iput(dir); |
| return -ENOENT; |
| } |
| if (!permission(dir,MAY_WRITE)) { |
| iput(dir); |
| return -EACCES; |
| } |
| if (!dir->i_op || !dir->i_op->rmdir) { |
| iput(dir); |
| return -EPERM; |
| } |
| return dir->i_op->rmdir(dir,basename,namelen); |
| } |
| |
| int sys_unlink(const char * name) |
| { |
| const char * basename; |
| int namelen; |
| struct inode * dir; |
| |
| if (!(dir = dir_namei(name,&namelen,&basename, NULL))) |
| return -ENOENT; |
| if (!namelen) { |
| iput(dir); |
| return -EPERM; |
| } |
| if (!permission(dir,MAY_WRITE)) { |
| iput(dir); |
| return -EACCES; |
| } |
| if (!dir->i_op || !dir->i_op->unlink) { |
| iput(dir); |
| return -EPERM; |
| } |
| return dir->i_op->unlink(dir,basename,namelen); |
| } |
| |
| int sys_symlink(const char * oldname, const char * newname) |
| { |
| struct inode * dir; |
| const char * basename; |
| int namelen; |
| |
| dir = dir_namei(newname,&namelen,&basename, NULL); |
| if (!dir) |
| return -ENOENT; |
| if (!namelen) { |
| iput(dir); |
| return -ENOENT; |
| } |
| if (!permission(dir,MAY_WRITE)) { |
| iput(dir); |
| return -EACCES; |
| } |
| if (!dir->i_op || !dir->i_op->symlink) { |
| iput(dir); |
| return -EPERM; |
| } |
| return dir->i_op->symlink(dir,basename,namelen,oldname); |
| } |
| |
| int sys_link(const char * oldname, const char * newname) |
| { |
| struct inode * oldinode, * dir; |
| const char * basename; |
| int namelen; |
| |
| oldinode = namei(oldname); |
| if (!oldinode) |
| return -ENOENT; |
| dir = dir_namei(newname,&namelen,&basename, NULL); |
| if (!dir) { |
| iput(oldinode); |
| return -EACCES; |
| } |
| if (!namelen) { |
| iput(oldinode); |
| iput(dir); |
| return -EPERM; |
| } |
| if (dir->i_dev != oldinode->i_dev) { |
| iput(dir); |
| iput(oldinode); |
| return -EXDEV; |
| } |
| if (!permission(dir,MAY_WRITE)) { |
| iput(dir); |
| iput(oldinode); |
| return -EACCES; |
| } |
| if (!dir->i_op || !dir->i_op->link) { |
| iput(dir); |
| iput(oldinode); |
| return -EPERM; |
| } |
| return dir->i_op->link(oldinode, dir, basename, namelen); |
| } |
| |
| int sys_rename(const char * oldname, const char * newname) |
| { |
| struct inode * old_dir, * new_dir; |
| const char * old_base, * new_base; |
| int old_len, new_len; |
| |
| old_dir = dir_namei(oldname,&old_len,&old_base, NULL); |
| if (!old_dir) |
| return -ENOENT; |
| if (!permission(old_dir,MAY_WRITE)) { |
| iput(old_dir); |
| return -EACCES; |
| } |
| if (!old_len || (get_fs_byte(old_base) == '.' && |
| (old_len == 1 || (get_fs_byte(old_base+1) == '.' && |
| old_len == 2)))) { |
| iput(old_dir); |
| return -EPERM; |
| } |
| new_dir = dir_namei(newname,&new_len,&new_base, NULL); |
| if (!new_dir) { |
| iput(old_dir); |
| return -ENOENT; |
| } |
| if (!permission(new_dir,MAY_WRITE)) { |
| iput(old_dir); |
| iput(new_dir); |
| return -EACCES; |
| } |
| if (!new_len || (get_fs_byte(new_base) == '.' && |
| (new_len == 1 || (get_fs_byte(new_base+1) == '.' && |
| new_len == 2)))) { |
| iput(old_dir); |
| iput(new_dir); |
| return -EPERM; |
| } |
| if (new_dir->i_dev != old_dir->i_dev) { |
| iput(old_dir); |
| iput(new_dir); |
| return -EXDEV; |
| } |
| if (!old_dir->i_op || !old_dir->i_op->rename) { |
| iput(old_dir); |
| iput(new_dir); |
| return -EPERM; |
| } |
| return old_dir->i_op->rename(old_dir, old_base, old_len, |
| new_dir, new_base, new_len); |
| } |