74ce793bcb
hostfs creates a new inode for each opened or created file, which created useless inode allocations and forbade identifying a host file with a kernel inode. Fix this uncommon filesystem behavior by tying kernel inodes to host file's inode and device IDs. Even if the host filesystem inodes may be recycled, this cannot happen while a file referencing it is opened, which is the case with hostfs. It should be noted that hostfs inode IDs may not be unique for the same hostfs superblock because multiple host's (backed) superblocks may be used. Delete inodes when dropping them to force backed host's file descriptors closing. This enables to entirely remove ARCH_EPHEMERAL_INODES, and then makes Landlock fully supported by UML. This is very useful for testing changes. These changes also factor out and simplify some helpers thanks to the new hostfs_inode_update() and the hostfs_iget() revamp: read_name(), hostfs_create(), hostfs_lookup(), hostfs_mknod(), and hostfs_fill_sb_common(). A following commit with new Landlock tests check this new hostfs inode consistency. Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com> Cc: Johannes Berg <johannes@sipsolutions.net> Acked-by: Richard Weinberger <richard@nod.at> Link: https://lore.kernel.org/r/20230612191430.339153-2-mic@digikod.net Signed-off-by: Mickaël Salaün <mic@digikod.net>
105 lines
3.5 KiB
C
105 lines
3.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __UM_FS_HOSTFS
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#define __UM_FS_HOSTFS
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#include <os.h>
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/*
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* These are exactly the same definitions as in fs.h, but the names are
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* changed so that this file can be included in both kernel and user files.
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*/
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#define HOSTFS_ATTR_MODE 1
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#define HOSTFS_ATTR_UID 2
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#define HOSTFS_ATTR_GID 4
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#define HOSTFS_ATTR_SIZE 8
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#define HOSTFS_ATTR_ATIME 16
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#define HOSTFS_ATTR_MTIME 32
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#define HOSTFS_ATTR_CTIME 64
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#define HOSTFS_ATTR_ATIME_SET 128
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#define HOSTFS_ATTR_MTIME_SET 256
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/* This one is unused by hostfs. */
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#define HOSTFS_ATTR_FORCE 512 /* Not a change, but a change it */
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#define HOSTFS_ATTR_ATTR_FLAG 1024
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/*
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* If you are very careful, you'll notice that these two are missing:
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*
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* #define ATTR_KILL_SUID 2048
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* #define ATTR_KILL_SGID 4096
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*
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* and this is because they were added in 2.5 development.
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* Actually, they are not needed by most ->setattr() methods - they are set by
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* callers of notify_change() to notify that the setuid/setgid bits must be
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* dropped.
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* notify_change() will delete those flags, make sure attr->ia_valid & ATTR_MODE
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* is on, and remove the appropriate bits from attr->ia_mode (attr is a
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* "struct iattr *"). -BlaisorBlade
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*/
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struct hostfs_timespec {
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long long tv_sec;
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long long tv_nsec;
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};
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struct hostfs_iattr {
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unsigned int ia_valid;
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unsigned short ia_mode;
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uid_t ia_uid;
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gid_t ia_gid;
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loff_t ia_size;
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struct hostfs_timespec ia_atime;
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struct hostfs_timespec ia_mtime;
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struct hostfs_timespec ia_ctime;
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};
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struct hostfs_stat {
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unsigned long long ino;
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unsigned int mode;
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unsigned int nlink;
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unsigned int uid;
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unsigned int gid;
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unsigned long long size;
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struct hostfs_timespec atime, mtime, ctime;
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unsigned int blksize;
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unsigned long long blocks;
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unsigned int maj;
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unsigned int min;
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dev_t dev;
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};
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extern int stat_file(const char *path, struct hostfs_stat *p, int fd);
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extern int access_file(char *path, int r, int w, int x);
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extern int open_file(char *path, int r, int w, int append);
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extern void *open_dir(char *path, int *err_out);
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extern void seek_dir(void *stream, unsigned long long pos);
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extern char *read_dir(void *stream, unsigned long long *pos_out,
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unsigned long long *ino_out, int *len_out,
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unsigned int *type_out);
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extern void close_file(void *stream);
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extern int replace_file(int oldfd, int fd);
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extern void close_dir(void *stream);
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extern int read_file(int fd, unsigned long long *offset, char *buf, int len);
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extern int write_file(int fd, unsigned long long *offset, const char *buf,
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int len);
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extern int lseek_file(int fd, long long offset, int whence);
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extern int fsync_file(int fd, int datasync);
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extern int file_create(char *name, int mode);
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extern int set_attr(const char *file, struct hostfs_iattr *attrs, int fd);
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extern int make_symlink(const char *from, const char *to);
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extern int unlink_file(const char *file);
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extern int do_mkdir(const char *file, int mode);
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extern int hostfs_do_rmdir(const char *file);
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extern int do_mknod(const char *file, int mode, unsigned int major,
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unsigned int minor);
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extern int link_file(const char *to, const char *from);
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extern int hostfs_do_readlink(char *file, char *buf, int size);
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extern int rename_file(char *from, char *to);
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extern int rename2_file(char *from, char *to, unsigned int flags);
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extern int do_statfs(char *root, long *bsize_out, long long *blocks_out,
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long long *bfree_out, long long *bavail_out,
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long long *files_out, long long *ffree_out,
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void *fsid_out, int fsid_size, long *namelen_out);
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#endif
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