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qemu/hw/9pfs/9p-local.c
Greg Kurz 4751fd5328 9pfs: local: fix fchmodat_nofollow() limitations 
This function has to ensure it doesn't follow a symlink that could be used
to escape the virtfs directory. This could be easily achieved if fchmodat()
on linux honored the AT_SYMLINK_NOFOLLOW flag as described in POSIX, but
it doesn't. There was a tentative to implement a new fchmodat2() syscall
with the correct semantics:

https://patchwork.kernel.org/patch/9596301/

but it didn't gain much momentum. Also it was suggested to look at an O_PATH
based solution in the first place.

The current implementation covers most use-cases, but it notably fails if:
- the target path has access rights equal to 0000 (openat() returns EPERM),
  => once you've done chmod(0000) on a file, you can never chmod() again
- the target path is UNIX domain socket (openat() returns ENXIO)
  => bind() of UNIX domain sockets fails if the file is on 9pfs

The solution is to use O_PATH: openat() now succeeds in both cases, and we
can ensure the path isn't a symlink with fstat(). The associated entry in
"/proc/self/fd" can hence be safely passed to the regular chmod() syscall.

The previous behavior is kept for older systems that don't have O_PATH.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Zhi Yong Wu <zhiyong.wu@ucloud.cn>
Acked-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2017-08-10 14:36:11 +02:00

1558 lines
41 KiB
C
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/*
* 9p Posix callback
*
* Copyright IBM, Corp. 2010
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "9p.h"
#include "9p-local.h"
#include "9p-xattr.h"
#include "9p-util.h"
#include "fsdev/qemu-fsdev.h" /* local_ops */
#include <arpa/inet.h>
#include <pwd.h>
#include <grp.h>
#include <sys/socket.h>
#include <sys/un.h>
#include "qemu/xattr.h"
#include "qemu/cutils.h"
#include "qemu/error-report.h"
#include <libgen.h>
#include <linux/fs.h>
#ifdef CONFIG_LINUX_MAGIC_H
#include <linux/magic.h>
#endif
#include <sys/ioctl.h>
#ifndef XFS_SUPER_MAGIC
#define XFS_SUPER_MAGIC 0x58465342
#endif
#ifndef EXT2_SUPER_MAGIC
#define EXT2_SUPER_MAGIC 0xEF53
#endif
#ifndef REISERFS_SUPER_MAGIC
#define REISERFS_SUPER_MAGIC 0x52654973
#endif
#ifndef BTRFS_SUPER_MAGIC
#define BTRFS_SUPER_MAGIC 0x9123683E
#endif
typedef struct {
int mountfd;
} LocalData;
int local_open_nofollow(FsContext *fs_ctx, const char *path, int flags,
mode_t mode)
{
LocalData *data = fs_ctx->private;
int fd = data->mountfd;
while (*path && fd != -1) {
const char *c;
int next_fd;
char *head;
/* Only relative paths without consecutive slashes */
assert(*path != '/');
head = g_strdup(path);
c = strchrnul(path, '/');
if (*c) {
/* Intermediate path element */
head[c - path] = 0;
path = c + 1;
next_fd = openat_dir(fd, head);
} else {
/* Rightmost path element */
next_fd = openat_file(fd, head, flags, mode);
path = c;
}
g_free(head);
if (fd != data->mountfd) {
close_preserve_errno(fd);
}
fd = next_fd;
}
assert(fd != data->mountfd);
return fd;
}
int local_opendir_nofollow(FsContext *fs_ctx, const char *path)
{
return local_open_nofollow(fs_ctx, path, O_DIRECTORY | O_RDONLY, 0);
}
static void renameat_preserve_errno(int odirfd, const char *opath, int ndirfd,
const char *npath)
{
int serrno = errno;
renameat(odirfd, opath, ndirfd, npath);
errno = serrno;
}
static void unlinkat_preserve_errno(int dirfd, const char *path, int flags)
{
int serrno = errno;
unlinkat(dirfd, path, flags);
errno = serrno;
}
#define VIRTFS_META_DIR ".virtfs_metadata"
#define VIRTFS_META_ROOT_FILE VIRTFS_META_DIR "_root"
static FILE *local_fopenat(int dirfd, const char *name, const char *mode)
{
int fd, o_mode = 0;
FILE *fp;
int flags;
/*
* only supports two modes
*/
if (mode[0] == 'r') {
flags = O_RDONLY;
} else if (mode[0] == 'w') {
flags = O_WRONLY | O_TRUNC | O_CREAT;
o_mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
} else {
return NULL;
}
fd = openat_file(dirfd, name, flags, o_mode);
if (fd == -1) {
return NULL;
}
fp = fdopen(fd, mode);
if (!fp) {
close(fd);
}
return fp;
}
#define ATTR_MAX 100
static void local_mapped_file_attr(int dirfd, const char *name,
struct stat *stbuf)
{
FILE *fp;
char buf[ATTR_MAX];
int map_dirfd;
if (strcmp(name, ".")) {
map_dirfd = openat_dir(dirfd, VIRTFS_META_DIR);
if (map_dirfd == -1) {
return;
}
fp = local_fopenat(map_dirfd, name, "r");
close_preserve_errno(map_dirfd);
} else {
fp = local_fopenat(dirfd, VIRTFS_META_ROOT_FILE, "r");
}
if (!fp) {
return;
}
memset(buf, 0, ATTR_MAX);
while (fgets(buf, ATTR_MAX, fp)) {
if (!strncmp(buf, "virtfs.uid", 10)) {
stbuf->st_uid = atoi(buf+11);
} else if (!strncmp(buf, "virtfs.gid", 10)) {
stbuf->st_gid = atoi(buf+11);
} else if (!strncmp(buf, "virtfs.mode", 11)) {
stbuf->st_mode = atoi(buf+12);
} else if (!strncmp(buf, "virtfs.rdev", 11)) {
stbuf->st_rdev = atoi(buf+12);
}
memset(buf, 0, ATTR_MAX);
}
fclose(fp);
}
static int local_lstat(FsContext *fs_ctx, V9fsPath *fs_path, struct stat *stbuf)
{
int err = -1;
char *dirpath = g_path_get_dirname(fs_path->data);
char *name = g_path_get_basename(fs_path->data);
int dirfd;
dirfd = local_opendir_nofollow(fs_ctx, dirpath);
if (dirfd == -1) {
goto out;
}
err = fstatat(dirfd, name, stbuf, AT_SYMLINK_NOFOLLOW);
if (err) {
goto err_out;
}
if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
/* Actual credentials are part of extended attrs */
uid_t tmp_uid;
gid_t tmp_gid;
mode_t tmp_mode;
dev_t tmp_dev;
if (fgetxattrat_nofollow(dirfd, name, "user.virtfs.uid", &tmp_uid,
sizeof(uid_t)) > 0) {
stbuf->st_uid = le32_to_cpu(tmp_uid);
}
if (fgetxattrat_nofollow(dirfd, name, "user.virtfs.gid", &tmp_gid,
sizeof(gid_t)) > 0) {
stbuf->st_gid = le32_to_cpu(tmp_gid);
}
if (fgetxattrat_nofollow(dirfd, name, "user.virtfs.mode", &tmp_mode,
sizeof(mode_t)) > 0) {
stbuf->st_mode = le32_to_cpu(tmp_mode);
}
if (fgetxattrat_nofollow(dirfd, name, "user.virtfs.rdev", &tmp_dev,
sizeof(dev_t)) > 0) {
stbuf->st_rdev = le64_to_cpu(tmp_dev);
}
} else if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
local_mapped_file_attr(dirfd, name, stbuf);
}
err_out:
close_preserve_errno(dirfd);
out:
g_free(name);
g_free(dirpath);
return err;
}
static int local_set_mapped_file_attrat(int dirfd, const char *name,
FsCred *credp)
{
FILE *fp;
int ret;
char buf[ATTR_MAX];
int uid = -1, gid = -1, mode = -1, rdev = -1;
int map_dirfd = -1, map_fd;
bool is_root = !strcmp(name, ".");
if (is_root) {
fp = local_fopenat(dirfd, VIRTFS_META_ROOT_FILE, "r");
if (!fp) {
if (errno == ENOENT) {
goto update_map_file;
} else {
return -1;
}
}
} else {
ret = mkdirat(dirfd, VIRTFS_META_DIR, 0700);
if (ret < 0 && errno != EEXIST) {
return -1;
}
map_dirfd = openat_dir(dirfd, VIRTFS_META_DIR);
if (map_dirfd == -1) {
return -1;
}
fp = local_fopenat(map_dirfd, name, "r");
if (!fp) {
if (errno == ENOENT) {
goto update_map_file;
} else {
close_preserve_errno(map_dirfd);
return -1;
}
}
}
memset(buf, 0, ATTR_MAX);
while (fgets(buf, ATTR_MAX, fp)) {
if (!strncmp(buf, "virtfs.uid", 10)) {
uid = atoi(buf + 11);
} else if (!strncmp(buf, "virtfs.gid", 10)) {
gid = atoi(buf + 11);
} else if (!strncmp(buf, "virtfs.mode", 11)) {
mode = atoi(buf + 12);
} else if (!strncmp(buf, "virtfs.rdev", 11)) {
rdev = atoi(buf + 12);
}
memset(buf, 0, ATTR_MAX);
}
fclose(fp);
update_map_file:
if (is_root) {
fp = local_fopenat(dirfd, VIRTFS_META_ROOT_FILE, "w");
} else {
fp = local_fopenat(map_dirfd, name, "w");
/* We can't go this far with map_dirfd not being a valid file descriptor
* but some versions of gcc aren't smart enough to see it.
*/
if (map_dirfd != -1) {
close_preserve_errno(map_dirfd);
}
}
if (!fp) {
return -1;
}
map_fd = fileno(fp);
assert(map_fd != -1);
ret = fchmod(map_fd, 0600);
assert(ret == 0);
if (credp->fc_uid != -1) {
uid = credp->fc_uid;
}
if (credp->fc_gid != -1) {
gid = credp->fc_gid;
}
if (credp->fc_mode != -1) {
mode = credp->fc_mode;
}
if (credp->fc_rdev != -1) {
rdev = credp->fc_rdev;
}
if (uid != -1) {
fprintf(fp, "virtfs.uid=%d\n", uid);
}
if (gid != -1) {
fprintf(fp, "virtfs.gid=%d\n", gid);
}
if (mode != -1) {
fprintf(fp, "virtfs.mode=%d\n", mode);
}
if (rdev != -1) {
fprintf(fp, "virtfs.rdev=%d\n", rdev);
}
fclose(fp);
return 0;
}
static int fchmodat_nofollow(int dirfd, const char *name, mode_t mode)
{
struct stat stbuf;
int fd, ret;
/* FIXME: this should be handled with fchmodat(AT_SYMLINK_NOFOLLOW).
* Unfortunately, the linux kernel doesn't implement it yet.
*/
/* First, we clear non-racing symlinks out of the way. */
if (fstatat(dirfd, name, &stbuf, AT_SYMLINK_NOFOLLOW)) {
return -1;
}
if (S_ISLNK(stbuf.st_mode)) {
errno = ELOOP;
return -1;
}
/* Access modes are ignored when O_PATH is supported. We try O_RDONLY and
* O_WRONLY for old-systems that don't support O_PATH.
*/
fd = openat_file(dirfd, name, O_RDONLY | O_PATH_9P_UTIL, 0);
#if O_PATH_9P_UTIL == 0
if (fd == -1) {
/* In case the file is writable-only and isn't a directory. */
if (errno == EACCES) {
fd = openat_file(dirfd, name, O_WRONLY, 0);
}
if (fd == -1 && errno == EISDIR) {
errno = EACCES;
}
}
if (fd == -1) {
return -1;
}
ret = fchmod(fd, mode);
#else
if (fd == -1) {
return -1;
}
/* Now we handle racing symlinks. */
ret = fstat(fd, &stbuf);
if (!ret) {
if (S_ISLNK(stbuf.st_mode)) {
errno = ELOOP;
ret = -1;
} else {
char *proc_path = g_strdup_printf("/proc/self/fd/%d", fd);
ret = chmod(proc_path, mode);
g_free(proc_path);
}
}
#endif
close_preserve_errno(fd);
return ret;
}
static int local_set_xattrat(int dirfd, const char *path, FsCred *credp)
{
int err;
if (credp->fc_uid != -1) {
uint32_t tmp_uid = cpu_to_le32(credp->fc_uid);
err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.uid", &tmp_uid,
sizeof(uid_t), 0);
if (err) {
return err;
}
}
if (credp->fc_gid != -1) {
uint32_t tmp_gid = cpu_to_le32(credp->fc_gid);
err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.gid", &tmp_gid,
sizeof(gid_t), 0);
if (err) {
return err;
}
}
if (credp->fc_mode != -1) {
uint32_t tmp_mode = cpu_to_le32(credp->fc_mode);
err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.mode", &tmp_mode,
sizeof(mode_t), 0);
if (err) {
return err;
}
}
if (credp->fc_rdev != -1) {
uint64_t tmp_rdev = cpu_to_le64(credp->fc_rdev);
err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.rdev", &tmp_rdev,
sizeof(dev_t), 0);
if (err) {
return err;
}
}
return 0;
}
static int local_set_cred_passthrough(FsContext *fs_ctx, int dirfd,
const char *name, FsCred *credp)
{
if (fchownat(dirfd, name, credp->fc_uid, credp->fc_gid,
AT_SYMLINK_NOFOLLOW) < 0) {
/*
* If we fail to change ownership and if we are
* using security model none. Ignore the error
*/
if ((fs_ctx->export_flags & V9FS_SEC_MASK) != V9FS_SM_NONE) {
return -1;
}
}
return fchmodat_nofollow(dirfd, name, credp->fc_mode & 07777);
}
static ssize_t local_readlink(FsContext *fs_ctx, V9fsPath *fs_path,
char *buf, size_t bufsz)
{
ssize_t tsize = -1;
if ((fs_ctx->export_flags & V9FS_SM_MAPPED) ||
(fs_ctx->export_flags & V9FS_SM_MAPPED_FILE)) {
int fd;
fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0);
if (fd == -1) {
return -1;
}
do {
tsize = read(fd, (void *)buf, bufsz);
} while (tsize == -1 && errno == EINTR);
close_preserve_errno(fd);
} else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
(fs_ctx->export_flags & V9FS_SM_NONE)) {
char *dirpath = g_path_get_dirname(fs_path->data);
char *name = g_path_get_basename(fs_path->data);
int dirfd;
dirfd = local_opendir_nofollow(fs_ctx, dirpath);
if (dirfd == -1) {
goto out;
}
tsize = readlinkat(dirfd, name, buf, bufsz);
close_preserve_errno(dirfd);
out:
g_free(name);
g_free(dirpath);
}
return tsize;
}
static int local_close(FsContext *ctx, V9fsFidOpenState *fs)
{
return close(fs->fd);
}
static int local_closedir(FsContext *ctx, V9fsFidOpenState *fs)
{
return closedir(fs->dir.stream);
}
static int local_open(FsContext *ctx, V9fsPath *fs_path,
int flags, V9fsFidOpenState *fs)
{
int fd;
fd = local_open_nofollow(ctx, fs_path->data, flags, 0);
if (fd == -1) {
return -1;
}
fs->fd = fd;
return fs->fd;
}
static int local_opendir(FsContext *ctx,
V9fsPath *fs_path, V9fsFidOpenState *fs)
{
int dirfd;
DIR *stream;
dirfd = local_opendir_nofollow(ctx, fs_path->data);
if (dirfd == -1) {
return -1;
}
stream = fdopendir(dirfd);
if (!stream) {
close(dirfd);
return -1;
}
fs->dir.stream = stream;
return 0;
}
static void local_rewinddir(FsContext *ctx, V9fsFidOpenState *fs)
{
rewinddir(fs->dir.stream);
}
static off_t local_telldir(FsContext *ctx, V9fsFidOpenState *fs)
{
return telldir(fs->dir.stream);
}
static bool local_is_mapped_file_metadata(FsContext *fs_ctx, const char *name)
{
return
!strcmp(name, VIRTFS_META_DIR) || !strcmp(name, VIRTFS_META_ROOT_FILE);
}
static struct dirent *local_readdir(FsContext *ctx, V9fsFidOpenState *fs)
{
struct dirent *entry;
again:
entry = readdir(fs->dir.stream);
if (!entry) {
return NULL;
}
if (ctx->export_flags & V9FS_SM_MAPPED) {
entry->d_type = DT_UNKNOWN;
} else if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
if (local_is_mapped_file_metadata(ctx, entry->d_name)) {
/* skip the meta data */
goto again;
}
entry->d_type = DT_UNKNOWN;
}
return entry;
}
static void local_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
{
seekdir(fs->dir.stream, off);
}
static ssize_t local_preadv(FsContext *ctx, V9fsFidOpenState *fs,
const struct iovec *iov,
int iovcnt, off_t offset)
{
#ifdef CONFIG_PREADV
return preadv(fs->fd, iov, iovcnt, offset);
#else
int err = lseek(fs->fd, offset, SEEK_SET);
if (err == -1) {
return err;
} else {
return readv(fs->fd, iov, iovcnt);
}
#endif
}
static ssize_t local_pwritev(FsContext *ctx, V9fsFidOpenState *fs,
const struct iovec *iov,
int iovcnt, off_t offset)
{
ssize_t ret;
#ifdef CONFIG_PREADV
ret = pwritev(fs->fd, iov, iovcnt, offset);
#else
int err = lseek(fs->fd, offset, SEEK_SET);
if (err == -1) {
return err;
} else {
ret = writev(fs->fd, iov, iovcnt);
}
#endif
#ifdef CONFIG_SYNC_FILE_RANGE
if (ret > 0 && ctx->export_flags & V9FS_IMMEDIATE_WRITEOUT) {
/*
* Initiate a writeback. This is not a data integrity sync.
* We want to ensure that we don't leave dirty pages in the cache
* after write when writeout=immediate is sepcified.
*/
sync_file_range(fs->fd, offset, ret,
SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE);
}
#endif
return ret;
}
static int local_chmod(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
{
char *dirpath = g_path_get_dirname(fs_path->data);
char *name = g_path_get_basename(fs_path->data);
int ret = -1;
int dirfd;
dirfd = local_opendir_nofollow(fs_ctx, dirpath);
if (dirfd == -1) {
goto out;
}
if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
ret = local_set_xattrat(dirfd, name, credp);
} else if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
ret = local_set_mapped_file_attrat(dirfd, name, credp);
} else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH ||
fs_ctx->export_flags & V9FS_SM_NONE) {
ret = fchmodat_nofollow(dirfd, name, credp->fc_mode);
}
close_preserve_errno(dirfd);
out:
g_free(dirpath);
g_free(name);
return ret;
}
static int local_mknod(FsContext *fs_ctx, V9fsPath *dir_path,
const char *name, FsCred *credp)
{
int err = -1;
int dirfd;
if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
local_is_mapped_file_metadata(fs_ctx, name)) {
errno = EINVAL;
return -1;
}
dirfd = local_opendir_nofollow(fs_ctx, dir_path->data);
if (dirfd == -1) {
return -1;
}
if (fs_ctx->export_flags & V9FS_SM_MAPPED ||
fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
err = mknodat(dirfd, name, fs_ctx->fmode | S_IFREG, 0);
if (err == -1) {
goto out;
}
if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
err = local_set_xattrat(dirfd, name, credp);
} else {
err = local_set_mapped_file_attrat(dirfd, name, credp);
}
if (err == -1) {
goto err_end;
}
} else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH ||
fs_ctx->export_flags & V9FS_SM_NONE) {
err = mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev);
if (err == -1) {
goto out;
}
err = local_set_cred_passthrough(fs_ctx, dirfd, name, credp);
if (err == -1) {
goto err_end;
}
}
goto out;
err_end:
unlinkat_preserve_errno(dirfd, name, 0);
out:
close_preserve_errno(dirfd);
return err;
}
static int local_mkdir(FsContext *fs_ctx, V9fsPath *dir_path,
const char *name, FsCred *credp)
{
int err = -1;
int dirfd;
if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
local_is_mapped_file_metadata(fs_ctx, name)) {
errno = EINVAL;
return -1;
}
dirfd = local_opendir_nofollow(fs_ctx, dir_path->data);
if (dirfd == -1) {
return -1;
}
if (fs_ctx->export_flags & V9FS_SM_MAPPED ||
fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
err = mkdirat(dirfd, name, fs_ctx->dmode);
if (err == -1) {
goto out;
}
credp->fc_mode = credp->fc_mode | S_IFDIR;
if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
err = local_set_xattrat(dirfd, name, credp);
} else {
err = local_set_mapped_file_attrat(dirfd, name, credp);
}
if (err == -1) {
goto err_end;
}
} else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH ||
fs_ctx->export_flags & V9FS_SM_NONE) {
err = mkdirat(dirfd, name, credp->fc_mode);
if (err == -1) {
goto out;
}
err = local_set_cred_passthrough(fs_ctx, dirfd, name, credp);
if (err == -1) {
goto err_end;
}
}
goto out;
err_end:
unlinkat_preserve_errno(dirfd, name, AT_REMOVEDIR);
out:
close_preserve_errno(dirfd);
return err;
}
static int local_fstat(FsContext *fs_ctx, int fid_type,
V9fsFidOpenState *fs, struct stat *stbuf)
{
int err, fd;
if (fid_type == P9_FID_DIR) {
fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
err = fstat(fd, stbuf);
if (err) {
return err;
}
if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
/* Actual credentials are part of extended attrs */
uid_t tmp_uid;
gid_t tmp_gid;
mode_t tmp_mode;
dev_t tmp_dev;
if (fgetxattr(fd, "user.virtfs.uid", &tmp_uid, sizeof(uid_t)) > 0) {
stbuf->st_uid = le32_to_cpu(tmp_uid);
}
if (fgetxattr(fd, "user.virtfs.gid", &tmp_gid, sizeof(gid_t)) > 0) {
stbuf->st_gid = le32_to_cpu(tmp_gid);
}
if (fgetxattr(fd, "user.virtfs.mode", &tmp_mode, sizeof(mode_t)) > 0) {
stbuf->st_mode = le32_to_cpu(tmp_mode);
}
if (fgetxattr(fd, "user.virtfs.rdev", &tmp_dev, sizeof(dev_t)) > 0) {
stbuf->st_rdev = le64_to_cpu(tmp_dev);
}
} else if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
errno = EOPNOTSUPP;
return -1;
}
return err;
}
static int local_open2(FsContext *fs_ctx, V9fsPath *dir_path, const char *name,
int flags, FsCred *credp, V9fsFidOpenState *fs)
{
int fd = -1;
int err = -1;
int dirfd;
if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
local_is_mapped_file_metadata(fs_ctx, name)) {
errno = EINVAL;
return -1;
}
/*
* Mark all the open to not follow symlinks
*/
flags |= O_NOFOLLOW;
dirfd = local_opendir_nofollow(fs_ctx, dir_path->data);
if (dirfd == -1) {
return -1;
}
/* Determine the security model */
if (fs_ctx->export_flags & V9FS_SM_MAPPED ||
fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
fd = openat_file(dirfd, name, flags, fs_ctx->fmode);
if (fd == -1) {
goto out;
}
credp->fc_mode = credp->fc_mode|S_IFREG;
if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
/* Set cleint credentials in xattr */
err = local_set_xattrat(dirfd, name, credp);
} else {
err = local_set_mapped_file_attrat(dirfd, name, credp);
}
if (err == -1) {
goto err_end;
}
} else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
(fs_ctx->export_flags & V9FS_SM_NONE)) {
fd = openat_file(dirfd, name, flags, credp->fc_mode);
if (fd == -1) {
goto out;
}
err = local_set_cred_passthrough(fs_ctx, dirfd, name, credp);
if (err == -1) {
goto err_end;
}
}
err = fd;
fs->fd = fd;
goto out;
err_end:
unlinkat_preserve_errno(dirfd, name,
flags & O_DIRECTORY ? AT_REMOVEDIR : 0);
close_preserve_errno(fd);
out:
close_preserve_errno(dirfd);
return err;
}
static int local_symlink(FsContext *fs_ctx, const char *oldpath,
V9fsPath *dir_path, const char *name, FsCred *credp)
{
int err = -1;
int dirfd;
if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
local_is_mapped_file_metadata(fs_ctx, name)) {
errno = EINVAL;
return -1;
}
dirfd = local_opendir_nofollow(fs_ctx, dir_path->data);
if (dirfd == -1) {
return -1;
}
/* Determine the security model */
if (fs_ctx->export_flags & V9FS_SM_MAPPED ||
fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
int fd;
ssize_t oldpath_size, write_size;
fd = openat_file(dirfd, name, O_CREAT | O_EXCL | O_RDWR,
fs_ctx->fmode);
if (fd == -1) {
goto out;
}
/* Write the oldpath (target) to the file. */
oldpath_size = strlen(oldpath);
do {
write_size = write(fd, (void *)oldpath, oldpath_size);
} while (write_size == -1 && errno == EINTR);
close_preserve_errno(fd);
if (write_size != oldpath_size) {
goto err_end;
}
/* Set cleint credentials in symlink's xattr */
credp->fc_mode = credp->fc_mode | S_IFLNK;
if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
err = local_set_xattrat(dirfd, name, credp);
} else {
err = local_set_mapped_file_attrat(dirfd, name, credp);
}
if (err == -1) {
goto err_end;
}
} else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH ||
fs_ctx->export_flags & V9FS_SM_NONE) {
err = symlinkat(oldpath, dirfd, name);
if (err) {
goto out;
}
err = fchownat(dirfd, name, credp->fc_uid, credp->fc_gid,
AT_SYMLINK_NOFOLLOW);
if (err == -1) {
/*
* If we fail to change ownership and if we are
* using security model none. Ignore the error
*/
if ((fs_ctx->export_flags & V9FS_SEC_MASK) != V9FS_SM_NONE) {
goto err_end;
} else {
err = 0;
}
}
}
goto out;
err_end:
unlinkat_preserve_errno(dirfd, name, 0);
out:
close_preserve_errno(dirfd);
return err;
}
static int local_link(FsContext *ctx, V9fsPath *oldpath,
V9fsPath *dirpath, const char *name)
{
char *odirpath = g_path_get_dirname(oldpath->data);
char *oname = g_path_get_basename(oldpath->data);
int ret = -1;
int odirfd, ndirfd;
if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
local_is_mapped_file_metadata(ctx, name)) {
errno = EINVAL;
return -1;
}
odirfd = local_opendir_nofollow(ctx, odirpath);
if (odirfd == -1) {
goto out;
}
ndirfd = local_opendir_nofollow(ctx, dirpath->data);
if (ndirfd == -1) {
close_preserve_errno(odirfd);
goto out;
}
ret = linkat(odirfd, oname, ndirfd, name, 0);
if (ret < 0) {
goto out_close;
}
/* now link the virtfs_metadata files */
if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
int omap_dirfd, nmap_dirfd;
ret = mkdirat(ndirfd, VIRTFS_META_DIR, 0700);
if (ret < 0 && errno != EEXIST) {
goto err_undo_link;
}
omap_dirfd = openat_dir(odirfd, VIRTFS_META_DIR);
if (omap_dirfd == -1) {
goto err;
}
nmap_dirfd = openat_dir(ndirfd, VIRTFS_META_DIR);
if (nmap_dirfd == -1) {
close_preserve_errno(omap_dirfd);
goto err;
}
ret = linkat(omap_dirfd, oname, nmap_dirfd, name, 0);
close_preserve_errno(nmap_dirfd);
close_preserve_errno(omap_dirfd);
if (ret < 0 && errno != ENOENT) {
goto err_undo_link;
}
ret = 0;
}
goto out_close;
err:
ret = -1;
err_undo_link:
unlinkat_preserve_errno(ndirfd, name, 0);
out_close:
close_preserve_errno(ndirfd);
close_preserve_errno(odirfd);
out:
g_free(oname);
g_free(odirpath);
return ret;
}
static int local_truncate(FsContext *ctx, V9fsPath *fs_path, off_t size)
{
int fd, ret;
fd = local_open_nofollow(ctx, fs_path->data, O_WRONLY, 0);
if (fd == -1) {
return -1;
}
ret = ftruncate(fd, size);
close_preserve_errno(fd);
return ret;
}
static int local_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
{
char *dirpath = g_path_get_dirname(fs_path->data);
char *name = g_path_get_basename(fs_path->data);
int ret = -1;
int dirfd;
dirfd = local_opendir_nofollow(fs_ctx, dirpath);
if (dirfd == -1) {
goto out;
}
if ((credp->fc_uid == -1 && credp->fc_gid == -1) ||
(fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
(fs_ctx->export_flags & V9FS_SM_NONE)) {
ret = fchownat(dirfd, name, credp->fc_uid, credp->fc_gid,
AT_SYMLINK_NOFOLLOW);
} else if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
ret = local_set_xattrat(dirfd, name, credp);
} else if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) {
ret = local_set_mapped_file_attrat(dirfd, name, credp);
}
close_preserve_errno(dirfd);
out:
g_free(name);
g_free(dirpath);
return ret;
}
static int local_utimensat(FsContext *s, V9fsPath *fs_path,
const struct timespec *buf)
{
char *dirpath = g_path_get_dirname(fs_path->data);
char *name = g_path_get_basename(fs_path->data);
int dirfd, ret = -1;
dirfd = local_opendir_nofollow(s, dirpath);
if (dirfd == -1) {
goto out;
}
ret = utimensat(dirfd, name, buf, AT_SYMLINK_NOFOLLOW);
close_preserve_errno(dirfd);
out:
g_free(dirpath);
g_free(name);
return ret;
}
static int local_unlinkat_common(FsContext *ctx, int dirfd, const char *name,
int flags)
{
int ret = -1;
if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
int map_dirfd;
/* We need to remove the metadata as well:
* - the metadata directory if we're removing a directory
* - the metadata file in the parent's metadata directory
*
* If any of these are missing (ie, ENOENT) then we're probably
* trying to remove something that wasn't created in mapped-file
* mode. We just ignore the error.
*/
if (flags == AT_REMOVEDIR) {
int fd;
fd = openat_dir(dirfd, name);
if (fd == -1) {
goto err_out;
}
ret = unlinkat(fd, VIRTFS_META_DIR, AT_REMOVEDIR);
close_preserve_errno(fd);
if (ret < 0 && errno != ENOENT) {
goto err_out;
}
}
map_dirfd = openat_dir(dirfd, VIRTFS_META_DIR);
if (map_dirfd != -1) {
ret = unlinkat(map_dirfd, name, 0);
close_preserve_errno(map_dirfd);
if (ret < 0 && errno != ENOENT) {
goto err_out;
}
} else if (errno != ENOENT) {
goto err_out;
}
}
ret = unlinkat(dirfd, name, flags);
err_out:
return ret;
}
static int local_remove(FsContext *ctx, const char *path)
{
struct stat stbuf;
char *dirpath = g_path_get_dirname(path);
char *name = g_path_get_basename(path);
int flags = 0;
int dirfd;
int err = -1;
dirfd = local_opendir_nofollow(ctx, dirpath);
if (dirfd == -1) {
goto out;
}
if (fstatat(dirfd, name, &stbuf, AT_SYMLINK_NOFOLLOW) < 0) {
goto err_out;
}
if (S_ISDIR(stbuf.st_mode)) {
flags |= AT_REMOVEDIR;
}
err = local_unlinkat_common(ctx, dirfd, name, flags);
err_out:
close_preserve_errno(dirfd);
out:
g_free(name);
g_free(dirpath);
return err;
}
static int local_fsync(FsContext *ctx, int fid_type,
V9fsFidOpenState *fs, int datasync)
{
int fd;
if (fid_type == P9_FID_DIR) {
fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
if (datasync) {
return qemu_fdatasync(fd);
} else {
return fsync(fd);
}
}
static int local_statfs(FsContext *s, V9fsPath *fs_path, struct statfs *stbuf)
{
int fd, ret;
fd = local_open_nofollow(s, fs_path->data, O_RDONLY, 0);
if (fd == -1) {
return -1;
}
ret = fstatfs(fd, stbuf);
close_preserve_errno(fd);
return ret;
}
static ssize_t local_lgetxattr(FsContext *ctx, V9fsPath *fs_path,
const char *name, void *value, size_t size)
{
char *path = fs_path->data;
return v9fs_get_xattr(ctx, path, name, value, size);
}
static ssize_t local_llistxattr(FsContext *ctx, V9fsPath *fs_path,
void *value, size_t size)
{
char *path = fs_path->data;
return v9fs_list_xattr(ctx, path, value, size);
}
static int local_lsetxattr(FsContext *ctx, V9fsPath *fs_path, const char *name,
void *value, size_t size, int flags)
{
char *path = fs_path->data;
return v9fs_set_xattr(ctx, path, name, value, size, flags);
}
static int local_lremovexattr(FsContext *ctx, V9fsPath *fs_path,
const char *name)
{
char *path = fs_path->data;
return v9fs_remove_xattr(ctx, path, name);
}
static int local_name_to_path(FsContext *ctx, V9fsPath *dir_path,
const char *name, V9fsPath *target)
{
if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
local_is_mapped_file_metadata(ctx, name)) {
errno = EINVAL;
return -1;
}
if (dir_path) {
if (!strcmp(name, ".")) {
/* "." relative to "foo/bar" is "foo/bar" */
v9fs_path_copy(target, dir_path);
} else if (!strcmp(name, "..")) {
if (!strcmp(dir_path->data, ".")) {
/* ".." relative to the root is "." */
v9fs_path_sprintf(target, ".");
} else {
char *tmp = g_path_get_dirname(dir_path->data);
/* Symbolic links are resolved by the client. We can assume
* that ".." relative to "foo/bar" is equivalent to "foo"
*/
v9fs_path_sprintf(target, "%s", tmp);
g_free(tmp);
}
} else {
assert(!strchr(name, '/'));
v9fs_path_sprintf(target, "%s/%s", dir_path->data, name);
}
} else if (!strcmp(name, "/") || !strcmp(name, ".") ||
!strcmp(name, "..")) {
/* This is the root fid */
v9fs_path_sprintf(target, ".");
} else {
assert(!strchr(name, '/'));
v9fs_path_sprintf(target, "./%s", name);
}
return 0;
}
static int local_renameat(FsContext *ctx, V9fsPath *olddir,
const char *old_name, V9fsPath *newdir,
const char *new_name)
{
int ret;
int odirfd, ndirfd;
if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
(local_is_mapped_file_metadata(ctx, old_name) ||
local_is_mapped_file_metadata(ctx, new_name))) {
errno = EINVAL;
return -1;
}
odirfd = local_opendir_nofollow(ctx, olddir->data);
if (odirfd == -1) {
return -1;
}
ndirfd = local_opendir_nofollow(ctx, newdir->data);
if (ndirfd == -1) {
close_preserve_errno(odirfd);
return -1;
}
ret = renameat(odirfd, old_name, ndirfd, new_name);
if (ret < 0) {
goto out;
}
if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
int omap_dirfd, nmap_dirfd;
ret = mkdirat(ndirfd, VIRTFS_META_DIR, 0700);
if (ret < 0 && errno != EEXIST) {
goto err_undo_rename;
}
omap_dirfd = openat_dir(odirfd, VIRTFS_META_DIR);
if (omap_dirfd == -1) {
goto err;
}
nmap_dirfd = openat_dir(ndirfd, VIRTFS_META_DIR);
if (nmap_dirfd == -1) {
close_preserve_errno(omap_dirfd);
goto err;
}
/* rename the .virtfs_metadata files */
ret = renameat(omap_dirfd, old_name, nmap_dirfd, new_name);
close_preserve_errno(nmap_dirfd);
close_preserve_errno(omap_dirfd);
if (ret < 0 && errno != ENOENT) {
goto err_undo_rename;
}
ret = 0;
}
goto out;
err:
ret = -1;
err_undo_rename:
renameat_preserve_errno(ndirfd, new_name, odirfd, old_name);
out:
close_preserve_errno(ndirfd);
close_preserve_errno(odirfd);
return ret;
}
static void v9fs_path_init_dirname(V9fsPath *path, const char *str)
{
path->data = g_path_get_dirname(str);
path->size = strlen(path->data) + 1;
}
static int local_rename(FsContext *ctx, const char *oldpath,
const char *newpath)
{
int err;
char *oname = g_path_get_basename(oldpath);
char *nname = g_path_get_basename(newpath);
V9fsPath olddir, newdir;
v9fs_path_init_dirname(&olddir, oldpath);
v9fs_path_init_dirname(&newdir, newpath);
err = local_renameat(ctx, &olddir, oname, &newdir, nname);
v9fs_path_free(&newdir);
v9fs_path_free(&olddir);
g_free(nname);
g_free(oname);
return err;
}
static int local_unlinkat(FsContext *ctx, V9fsPath *dir,
const char *name, int flags)
{
int ret;
int dirfd;
if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
local_is_mapped_file_metadata(ctx, name)) {
errno = EINVAL;
return -1;
}
dirfd = local_opendir_nofollow(ctx, dir->data);
if (dirfd == -1) {
return -1;
}
ret = local_unlinkat_common(ctx, dirfd, name, flags);
close_preserve_errno(dirfd);
return ret;
}
static int local_ioc_getversion(FsContext *ctx, V9fsPath *path,
mode_t st_mode, uint64_t *st_gen)
{
#ifdef FS_IOC_GETVERSION
int err;
V9fsFidOpenState fid_open;
/*
* Do not try to open special files like device nodes, fifos etc
* We can get fd for regular files and directories only
*/
if (!S_ISREG(st_mode) && !S_ISDIR(st_mode)) {
errno = ENOTTY;
return -1;
}
err = local_open(ctx, path, O_RDONLY, &fid_open);
if (err < 0) {
return err;
}
err = ioctl(fid_open.fd, FS_IOC_GETVERSION, st_gen);
local_close(ctx, &fid_open);
return err;
#else
errno = ENOTTY;
return -1;
#endif
}
static int local_init(FsContext *ctx)
{
struct statfs stbuf;
LocalData *data = g_malloc(sizeof(*data));
data->mountfd = open(ctx->fs_root, O_DIRECTORY | O_RDONLY);
if (data->mountfd == -1) {
goto err;
}
#ifdef FS_IOC_GETVERSION
/*
* use ioc_getversion only if the ioctl is definied
*/
if (fstatfs(data->mountfd, &stbuf) < 0) {
close_preserve_errno(data->mountfd);
goto err;
}
switch (stbuf.f_type) {
case EXT2_SUPER_MAGIC:
case BTRFS_SUPER_MAGIC:
case REISERFS_SUPER_MAGIC:
case XFS_SUPER_MAGIC:
ctx->exops.get_st_gen = local_ioc_getversion;
break;
}
#endif
if (ctx->export_flags & V9FS_SM_PASSTHROUGH) {
ctx->xops = passthrough_xattr_ops;
} else if (ctx->export_flags & V9FS_SM_MAPPED) {
ctx->xops = mapped_xattr_ops;
} else if (ctx->export_flags & V9FS_SM_NONE) {
ctx->xops = none_xattr_ops;
} else if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
/*
* xattr operation for mapped-file and passthrough
* remain same.
*/
ctx->xops = passthrough_xattr_ops;
}
ctx->export_flags |= V9FS_PATHNAME_FSCONTEXT;
ctx->private = data;
return 0;
err:
g_free(data);
return -1;
}
static void local_cleanup(FsContext *ctx)
{
LocalData *data = ctx->private;
close(data->mountfd);
g_free(data);
}
static int local_parse_opts(QemuOpts *opts, struct FsDriverEntry *fse)
{
const char *sec_model = qemu_opt_get(opts, "security_model");
const char *path = qemu_opt_get(opts, "path");
Error *err = NULL;
if (!sec_model) {
error_report("Security model not specified, local fs needs security model");
error_printf("valid options are:"
"\tsecurity_model=[passthrough|mapped-xattr|mapped-file|none]\n");
return -1;
}
if (!strcmp(sec_model, "passthrough")) {
fse->export_flags |= V9FS_SM_PASSTHROUGH;
} else if (!strcmp(sec_model, "mapped") ||
!strcmp(sec_model, "mapped-xattr")) {
fse->export_flags |= V9FS_SM_MAPPED;
} else if (!strcmp(sec_model, "none")) {
fse->export_flags |= V9FS_SM_NONE;
} else if (!strcmp(sec_model, "mapped-file")) {
fse->export_flags |= V9FS_SM_MAPPED_FILE;
} else {
error_report("Invalid security model %s specified", sec_model);
error_printf("valid options are:"
"\t[passthrough|mapped-xattr|mapped-file|none]\n");
return -1;
}
if (!path) {
error_report("fsdev: No path specified");
return -1;
}
fsdev_throttle_parse_opts(opts, &fse->fst, &err);
if (err) {
error_reportf_err(err, "Throttle configuration is not valid: ");
return -1;
}
if (fse->export_flags & V9FS_SM_MAPPED ||
fse->export_flags & V9FS_SM_MAPPED_FILE) {
fse->fmode =
qemu_opt_get_number(opts, "fmode", SM_LOCAL_MODE_BITS) & 0777;
fse->dmode =
qemu_opt_get_number(opts, "dmode", SM_LOCAL_DIR_MODE_BITS) & 0777;
} else {
if (qemu_opt_find(opts, "fmode")) {
error_report("fmode is only valid for mapped 9p modes");
return -1;
}
if (qemu_opt_find(opts, "dmode")) {
error_report("dmode is only valid for mapped 9p modes");
return -1;
}
}
fse->path = g_strdup(path);
return 0;
}
FileOperations local_ops = {
.parse_opts = local_parse_opts,
.init = local_init,
.cleanup = local_cleanup,
.lstat = local_lstat,
.readlink = local_readlink,
.close = local_close,
.closedir = local_closedir,
.open = local_open,
.opendir = local_opendir,
.rewinddir = local_rewinddir,
.telldir = local_telldir,
.readdir = local_readdir,
.seekdir = local_seekdir,
.preadv = local_preadv,
.pwritev = local_pwritev,
.chmod = local_chmod,
.mknod = local_mknod,
.mkdir = local_mkdir,
.fstat = local_fstat,
.open2 = local_open2,
.symlink = local_symlink,
.link = local_link,
.truncate = local_truncate,
.rename = local_rename,
.chown = local_chown,
.utimensat = local_utimensat,
.remove = local_remove,
.fsync = local_fsync,
.statfs = local_statfs,
.lgetxattr = local_lgetxattr,
.llistxattr = local_llistxattr,
.lsetxattr = local_lsetxattr,
.lremovexattr = local_lremovexattr,
.name_to_path = local_name_to_path,
.renameat = local_renameat,
.unlinkat = local_unlinkat,
};
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