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95d2715791
qemu/tools/virtiofsd/passthrough_ll.c
Miklos Szeredi 95d2715791 virtiofsd: rename unref_inode() to unref_inode_lolocked() 
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
2020-01-23 16:41:37 +00:00

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/*
* FUSE: Filesystem in Userspace
* Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
*
* This program can be distributed under the terms of the GNU GPLv2.
* See the file COPYING.
*/
/*
*
* This file system mirrors the existing file system hierarchy of the
* system, starting at the root file system. This is implemented by
* just "passing through" all requests to the corresponding user-space
* libc functions. In contrast to passthrough.c and passthrough_fh.c,
* this implementation uses the low-level API. Its performance should
* be the least bad among the three, but many operations are not
* implemented. In particular, it is not possible to remove files (or
* directories) because the code necessary to defer actual removal
* until the file is not opened anymore would make the example much
* more complicated.
*
* When writeback caching is enabled (-o writeback mount option), it
* is only possible to write to files for which the mounting user has
* read permissions. This is because the writeback cache requires the
* kernel to be able to issue read requests for all files (which the
* passthrough filesystem cannot satisfy if it can't read the file in
* the underlying filesystem).
*
* Compile with:
*
* gcc -Wall passthrough_ll.c `pkg-config fuse3 --cflags --libs` -o
* passthrough_ll
*
* ## Source code ##
* \include passthrough_ll.c
*/
#include "qemu/osdep.h"
#include "qemu/timer.h"
#include "fuse_virtio.h"
#include "fuse_log.h"
#include "fuse_lowlevel.h"
#include <assert.h>
#include <cap-ng.h>
#include <dirent.h>
#include <errno.h>
#include <glib.h>
#include <inttypes.h>
#include <limits.h>
#include <pthread.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/xattr.h>
#include <syslog.h>
#include <unistd.h>
#include "passthrough_helpers.h"
#include "seccomp.h"
struct lo_map_elem {
union {
struct lo_inode *inode;
struct lo_dirp *dirp;
int fd;
ssize_t freelist;
};
bool in_use;
};
/* Maps FUSE fh or ino values to internal objects */
struct lo_map {
struct lo_map_elem *elems;
size_t nelems;
ssize_t freelist;
};
struct lo_inode {
struct lo_inode *next; /* protected by lo->mutex */
struct lo_inode *prev; /* protected by lo->mutex */
int fd;
bool is_symlink;
ino_t ino;
dev_t dev;
uint64_t refcount; /* protected by lo->mutex */
fuse_ino_t fuse_ino;
};
struct lo_cred {
uid_t euid;
gid_t egid;
};
enum {
CACHE_NEVER,
CACHE_NORMAL,
CACHE_ALWAYS,
};
struct lo_data {
pthread_mutex_t mutex;
int debug;
int norace;
int writeback;
int flock;
int xattr;
const char *source;
double timeout;
int cache;
int timeout_set;
int readdirplus_set;
int readdirplus_clear;
struct lo_inode root; /* protected by lo->mutex */
struct lo_map ino_map; /* protected by lo->mutex */
struct lo_map dirp_map; /* protected by lo->mutex */
struct lo_map fd_map; /* protected by lo->mutex */
/* An O_PATH file descriptor to /proc/self/fd/ */
int proc_self_fd;
};
static const struct fuse_opt lo_opts[] = {
{ "writeback", offsetof(struct lo_data, writeback), 1 },
{ "no_writeback", offsetof(struct lo_data, writeback), 0 },
{ "source=%s", offsetof(struct lo_data, source), 0 },
{ "flock", offsetof(struct lo_data, flock), 1 },
{ "no_flock", offsetof(struct lo_data, flock), 0 },
{ "xattr", offsetof(struct lo_data, xattr), 1 },
{ "no_xattr", offsetof(struct lo_data, xattr), 0 },
{ "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
{ "timeout=", offsetof(struct lo_data, timeout_set), 1 },
{ "cache=never", offsetof(struct lo_data, cache), CACHE_NEVER },
{ "cache=auto", offsetof(struct lo_data, cache), CACHE_NORMAL },
{ "cache=always", offsetof(struct lo_data, cache), CACHE_ALWAYS },
{ "norace", offsetof(struct lo_data, norace), 1 },
{ "readdirplus", offsetof(struct lo_data, readdirplus_set), 1 },
{ "no_readdirplus", offsetof(struct lo_data, readdirplus_clear), 1 },
FUSE_OPT_END
};
static bool use_syslog = false;
static int current_log_level;
static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode,
uint64_t n);
static struct {
pthread_mutex_t mutex;
void *saved;
} cap;
/* That we loaded cap-ng in the current thread from the saved */
static __thread bool cap_loaded = 0;
static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st);
static int is_dot_or_dotdot(const char *name)
{
return name[0] == '.' &&
(name[1] == '\0' || (name[1] == '.' && name[2] == '\0'));
}
/* Is `path` a single path component that is not "." or ".."? */
static int is_safe_path_component(const char *path)
{
if (strchr(path, '/')) {
return 0;
}
return !is_dot_or_dotdot(path);
}
static struct lo_data *lo_data(fuse_req_t req)
{
return (struct lo_data *)fuse_req_userdata(req);
}
/*
* Load capng's state from our saved state if the current thread
* hadn't previously been loaded.
* returns 0 on success
*/
static int load_capng(void)
{
if (!cap_loaded) {
pthread_mutex_lock(&cap.mutex);
capng_restore_state(&cap.saved);
/*
* restore_state free's the saved copy
* so make another.
*/
cap.saved = capng_save_state();
if (!cap.saved) {
fuse_log(FUSE_LOG_ERR, "capng_save_state (thread)\n");
return -EINVAL;
}
pthread_mutex_unlock(&cap.mutex);
/*
* We want to use the loaded state for our pid,
* not the original
*/
capng_setpid(syscall(SYS_gettid));
cap_loaded = true;
}
return 0;
}
/*
* Helpers for dropping and regaining effective capabilities. Returns 0
* on success, error otherwise
*/
static int drop_effective_cap(const char *cap_name, bool *cap_dropped)
{
int cap, ret;
cap = capng_name_to_capability(cap_name);
if (cap < 0) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n",
cap_name, strerror(errno));
goto out;
}
if (load_capng()) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "load_capng() failed\n");
goto out;
}
/* We dont have this capability in effective set already. */
if (!capng_have_capability(CAPNG_EFFECTIVE, cap)) {
ret = 0;
goto out;
}
if (capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, cap)) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "capng_update(DROP,) failed\n");
goto out;
}
if (capng_apply(CAPNG_SELECT_CAPS)) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "drop:capng_apply() failed\n");
goto out;
}
ret = 0;
if (cap_dropped) {
*cap_dropped = true;
}
out:
return ret;
}
static int gain_effective_cap(const char *cap_name)
{
int cap;
int ret = 0;
cap = capng_name_to_capability(cap_name);
if (cap < 0) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n",
cap_name, strerror(errno));
goto out;
}
if (load_capng()) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "load_capng() failed\n");
goto out;
}
if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, cap)) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "capng_update(ADD,) failed\n");
goto out;
}
if (capng_apply(CAPNG_SELECT_CAPS)) {
ret = errno;
fuse_log(FUSE_LOG_ERR, "gain:capng_apply() failed\n");
goto out;
}
ret = 0;
out:
return ret;
}
static void lo_map_init(struct lo_map *map)
{
map->elems = NULL;
map->nelems = 0;
map->freelist = -1;
}
static void lo_map_destroy(struct lo_map *map)
{
free(map->elems);
}
static int lo_map_grow(struct lo_map *map, size_t new_nelems)
{
struct lo_map_elem *new_elems;
size_t i;
if (new_nelems <= map->nelems) {
return 1;
}
new_elems = realloc(map->elems, sizeof(map->elems[0]) * new_nelems);
if (!new_elems) {
return 0;
}
for (i = map->nelems; i < new_nelems; i++) {
new_elems[i].freelist = i + 1;
new_elems[i].in_use = false;
}
new_elems[new_nelems - 1].freelist = -1;
map->elems = new_elems;
map->freelist = map->nelems;
map->nelems = new_nelems;
return 1;
}
static struct lo_map_elem *lo_map_alloc_elem(struct lo_map *map)
{
struct lo_map_elem *elem;
if (map->freelist == -1 && !lo_map_grow(map, map->nelems + 256)) {
return NULL;
}
elem = &map->elems[map->freelist];
map->freelist = elem->freelist;
elem->in_use = true;
return elem;
}
static struct lo_map_elem *lo_map_reserve(struct lo_map *map, size_t key)
{
ssize_t *prev;
if (!lo_map_grow(map, key + 1)) {
return NULL;
}
for (prev = &map->freelist; *prev != -1;
prev = &map->elems[*prev].freelist) {
if (*prev == key) {
struct lo_map_elem *elem = &map->elems[key];
*prev = elem->freelist;
elem->in_use = true;
return elem;
}
}
return NULL;
}
static struct lo_map_elem *lo_map_get(struct lo_map *map, size_t key)
{
if (key >= map->nelems) {
return NULL;
}
if (!map->elems[key].in_use) {
return NULL;
}
return &map->elems[key];
}
static void lo_map_remove(struct lo_map *map, size_t key)
{
struct lo_map_elem *elem;
if (key >= map->nelems) {
return;
}
elem = &map->elems[key];
if (!elem->in_use) {
return;
}
elem->in_use = false;
elem->freelist = map->freelist;
map->freelist = key;
}
/* Assumes lo->mutex is held */
static ssize_t lo_add_fd_mapping(fuse_req_t req, int fd)
{
struct lo_map_elem *elem;
elem = lo_map_alloc_elem(&lo_data(req)->fd_map);
if (!elem) {
return -1;
}
elem->fd = fd;
return elem - lo_data(req)->fd_map.elems;
}
/* Assumes lo->mutex is held */
static ssize_t lo_add_dirp_mapping(fuse_req_t req, struct lo_dirp *dirp)
{
struct lo_map_elem *elem;
elem = lo_map_alloc_elem(&lo_data(req)->dirp_map);
if (!elem) {
return -1;
}
elem->dirp = dirp;
return elem - lo_data(req)->dirp_map.elems;
}
/* Assumes lo->mutex is held */
static ssize_t lo_add_inode_mapping(fuse_req_t req, struct lo_inode *inode)
{
struct lo_map_elem *elem;
elem = lo_map_alloc_elem(&lo_data(req)->ino_map);
if (!elem) {
return -1;
}
elem->inode = inode;
return elem - lo_data(req)->ino_map.elems;
}
static struct lo_inode *lo_inode(fuse_req_t req, fuse_ino_t ino)
{
struct lo_data *lo = lo_data(req);
struct lo_map_elem *elem;
pthread_mutex_lock(&lo->mutex);
elem = lo_map_get(&lo->ino_map, ino);
pthread_mutex_unlock(&lo->mutex);
if (!elem) {
return NULL;
}
return elem->inode;
}
static int lo_fd(fuse_req_t req, fuse_ino_t ino)
{
struct lo_inode *inode = lo_inode(req, ino);
return inode ? inode->fd : -1;
}
static void lo_init(void *userdata, struct fuse_conn_info *conn)
{
struct lo_data *lo = (struct lo_data *)userdata;
if (conn->capable & FUSE_CAP_EXPORT_SUPPORT) {
conn->want |= FUSE_CAP_EXPORT_SUPPORT;
}
if (lo->writeback && conn->capable & FUSE_CAP_WRITEBACK_CACHE) {
fuse_log(FUSE_LOG_DEBUG, "lo_init: activating writeback\n");
conn->want |= FUSE_CAP_WRITEBACK_CACHE;
}
if (lo->flock && conn->capable & FUSE_CAP_FLOCK_LOCKS) {
fuse_log(FUSE_LOG_DEBUG, "lo_init: activating flock locks\n");
conn->want |= FUSE_CAP_FLOCK_LOCKS;
}
if ((lo->cache == CACHE_NEVER && !lo->readdirplus_set) ||
lo->readdirplus_clear) {
fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling readdirplus\n");
conn->want &= ~FUSE_CAP_READDIRPLUS;
}
}
static void lo_getattr(fuse_req_t req, fuse_ino_t ino,
struct fuse_file_info *fi)
{
int res;
struct stat buf;
struct lo_data *lo = lo_data(req);
(void)fi;
res =
fstatat(lo_fd(req, ino), "", &buf, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
if (res == -1) {
return (void)fuse_reply_err(req, errno);
}
fuse_reply_attr(req, &buf, lo->timeout);
}
static int lo_parent_and_name(struct lo_data *lo, struct lo_inode *inode,
char path[PATH_MAX], struct lo_inode **parent)
{
char procname[64];
char *last;
struct stat stat;
struct lo_inode *p;
int retries = 2;
int res;
retry:
sprintf(procname, "%i", inode->fd);
res = readlinkat(lo->proc_self_fd, procname, path, PATH_MAX);
if (res < 0) {
fuse_log(FUSE_LOG_WARNING, "%s: readlink failed: %m\n", __func__);
goto fail_noretry;
}
if (res >= PATH_MAX) {
fuse_log(FUSE_LOG_WARNING, "%s: readlink overflowed\n", __func__);
goto fail_noretry;
}
path[res] = '\0';
last = strrchr(path, '/');
if (last == NULL) {
/* Shouldn't happen */
fuse_log(
FUSE_LOG_WARNING,
"%s: INTERNAL ERROR: bad path read from proc\n", __func__);
goto fail_noretry;
}
if (last == path) {
p = &lo->root;
pthread_mutex_lock(&lo->mutex);
p->refcount++;
pthread_mutex_unlock(&lo->mutex);
} else {
*last = '\0';
res = fstatat(AT_FDCWD, last == path ? "/" : path, &stat, 0);
if (res == -1) {
if (!retries) {
fuse_log(FUSE_LOG_WARNING,
"%s: failed to stat parent: %m\n", __func__);
}
goto fail;
}
p = lo_find(lo, &stat);
if (p == NULL) {
if (!retries) {
fuse_log(FUSE_LOG_WARNING,
"%s: failed to find parent\n", __func__);
}
goto fail;
}
}
last++;
res = fstatat(p->fd, last, &stat, AT_SYMLINK_NOFOLLOW);
if (res == -1) {
if (!retries) {
fuse_log(FUSE_LOG_WARNING,
"%s: failed to stat last\n", __func__);
}
goto fail_unref;
}
if (stat.st_dev != inode->dev || stat.st_ino != inode->ino) {
if (!retries) {
fuse_log(FUSE_LOG_WARNING,
"%s: failed to match last\n", __func__);
}
goto fail_unref;
}
*parent = p;
memmove(path, last, strlen(last) + 1);
return 0;
fail_unref:
unref_inode_lolocked(lo, p, 1);
fail:
if (retries) {
retries--;
goto retry;
}
fail_noretry:
errno = EIO;
return -1;
}
static int utimensat_empty(struct lo_data *lo, struct lo_inode *inode,
const struct timespec *tv)
{
int res;
struct lo_inode *parent;
char path[PATH_MAX];
if (inode->is_symlink) {
res = utimensat(inode->fd, "", tv, AT_EMPTY_PATH);
if (res == -1 && errno == EINVAL) {
/* Sorry, no race free way to set times on symlink. */
if (lo->norace) {
errno = EPERM;
} else {
goto fallback;
}
}
return res;
}
sprintf(path, "%i", inode->fd);
return utimensat(lo->proc_self_fd, path, tv, 0);
fallback:
res = lo_parent_and_name(lo, inode, path, &parent);
if (res != -1) {
res = utimensat(parent->fd, path, tv, AT_SYMLINK_NOFOLLOW);
unref_inode_lolocked(lo, parent, 1);
}
return res;
}
static int lo_fi_fd(fuse_req_t req, struct fuse_file_info *fi)
{
struct lo_data *lo = lo_data(req);
struct lo_map_elem *elem;
pthread_mutex_lock(&lo->mutex);
elem = lo_map_get(&lo->fd_map, fi->fh);
pthread_mutex_unlock(&lo->mutex);
if (!elem) {
return -1;
}
return elem->fd;
}
static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
int valid, struct fuse_file_info *fi)
{
int saverr;
char procname[64];
struct lo_data *lo = lo_data(req);
struct lo_inode *inode;
int ifd;
int res;
int fd;
inode = lo_inode(req, ino);
if (!inode) {
fuse_reply_err(req, EBADF);
return;
}
ifd = inode->fd;
/* If fi->fh is invalid we'll report EBADF later */
if (fi) {
fd = lo_fi_fd(req, fi);
}
if (valid & FUSE_SET_ATTR_MODE) {
if (fi) {
res = fchmod(fd, attr->st_mode);
} else {
sprintf(procname, "%i", ifd);
res = fchmodat(lo->proc_self_fd, procname, attr->st_mode, 0);
}
if (res == -1) {
goto out_err;
}
}
if (valid & (FUSE_SET_ATTR_UID | FUSE_SET_ATTR_GID)) {
uid_t uid = (valid & FUSE_SET_ATTR_UID) ? attr->st_uid : (uid_t)-1;
gid_t gid = (valid & FUSE_SET_ATTR_GID) ? attr->st_gid : (gid_t)-1;
res = fchownat(ifd, "", uid, gid, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
if (res == -1) {
goto out_err;
}
}
if (valid & FUSE_SET_ATTR_SIZE) {
int truncfd;
if (fi) {
truncfd = fd;
} else {
sprintf(procname, "%i", ifd);
truncfd = openat(lo->proc_self_fd, procname, O_RDWR);
if (truncfd < 0) {
goto out_err;
}
}
res = ftruncate(truncfd, attr->st_size);
if (!fi) {
saverr = errno;
close(truncfd);
errno = saverr;
}
if (res == -1) {
goto out_err;
}
}
if (valid & (FUSE_SET_ATTR_ATIME | FUSE_SET_ATTR_MTIME)) {
struct timespec tv[2];
tv[0].tv_sec = 0;
tv[1].tv_sec = 0;
tv[0].tv_nsec = UTIME_OMIT;
tv[1].tv_nsec = UTIME_OMIT;
if (valid & FUSE_SET_ATTR_ATIME_NOW) {
tv[0].tv_nsec = UTIME_NOW;
} else if (valid & FUSE_SET_ATTR_ATIME) {
tv[0] = attr->st_atim;
}
if (valid & FUSE_SET_ATTR_MTIME_NOW) {
tv[1].tv_nsec = UTIME_NOW;
} else if (valid & FUSE_SET_ATTR_MTIME) {
tv[1] = attr->st_mtim;
}
if (fi) {
res = futimens(fd, tv);
} else {
res = utimensat_empty(lo, inode, tv);
}
if (res == -1) {
goto out_err;
}
}
return lo_getattr(req, ino, fi);
out_err:
saverr = errno;
fuse_reply_err(req, saverr);
}
static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st)
{
struct lo_inode *p;
struct lo_inode *ret = NULL;
pthread_mutex_lock(&lo->mutex);
for (p = lo->root.next; p != &lo->root; p = p->next) {
if (p->ino == st->st_ino && p->dev == st->st_dev) {
assert(p->refcount > 0);
ret = p;
ret->refcount++;
break;
}
}
pthread_mutex_unlock(&lo->mutex);
return ret;
}
static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
struct fuse_entry_param *e)
{
int newfd;
int res;
int saverr;
struct lo_data *lo = lo_data(req);
struct lo_inode *inode, *dir = lo_inode(req, parent);
memset(e, 0, sizeof(*e));
e->attr_timeout = lo->timeout;
e->entry_timeout = lo->timeout;
/* Do not allow escaping root directory */
if (dir == &lo->root && strcmp(name, "..") == 0) {
name = ".";
}
newfd = openat(lo_fd(req, parent), name, O_PATH | O_NOFOLLOW);
if (newfd == -1) {
goto out_err;
}
res = fstatat(newfd, "", &e->attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
if (res == -1) {
goto out_err;
}
inode = lo_find(lo_data(req), &e->attr);
if (inode) {
close(newfd);
newfd = -1;
} else {
struct lo_inode *prev, *next;
saverr = ENOMEM;
inode = calloc(1, sizeof(struct lo_inode));
if (!inode) {
goto out_err;
}
inode->is_symlink = S_ISLNK(e->attr.st_mode);
inode->refcount = 1;
inode->fd = newfd;
inode->ino = e->attr.st_ino;
inode->dev = e->attr.st_dev;
pthread_mutex_lock(&lo->mutex);
inode->fuse_ino = lo_add_inode_mapping(req, inode);
prev = &lo->root;
next = prev->next;
next->prev = inode;
inode->next = next;
inode->prev = prev;
prev->next = inode;
pthread_mutex_unlock(&lo->mutex);
}
e->ino = inode->fuse_ino;
fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent,
name, (unsigned long long)e->ino);
return 0;
out_err:
saverr = errno;
if (newfd != -1) {
close(newfd);
}
return saverr;
}
static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
{
struct fuse_entry_param e;
int err;
fuse_log(FUSE_LOG_DEBUG, "lo_lookup(parent=%" PRIu64 ", name=%s)\n", parent,
name);
/*
* Don't use is_safe_path_component(), allow "." and ".." for NFS export
* support.
*/
if (strchr(name, '/')) {
fuse_reply_err(req, EINVAL);
return;
}
err = lo_do_lookup(req, parent, name, &e);
if (err) {
fuse_reply_err(req, err);
} else {
fuse_reply_entry(req, &e);
}
}
/*
* On some archs, setres*id is limited to 2^16 but they
* provide setres*id32 variants that allow 2^32.
* Others just let setres*id do 2^32 anyway.
*/
#ifdef SYS_setresgid32
#define OURSYS_setresgid SYS_setresgid32
#else
#define OURSYS_setresgid SYS_setresgid
#endif
#ifdef SYS_setresuid32
#define OURSYS_setresuid SYS_setresuid32
#else
#define OURSYS_setresuid SYS_setresuid
#endif
/*
* Change to uid/gid of caller so that file is created with
* ownership of caller.
* TODO: What about selinux context?
*/
static int lo_change_cred(fuse_req_t req, struct lo_cred *old)
{
int res;
old->euid = geteuid();
old->egid = getegid();
res = syscall(OURSYS_setresgid, -1, fuse_req_ctx(req)->gid, -1);
if (res == -1) {
return errno;
}
res = syscall(OURSYS_setresuid, -1, fuse_req_ctx(req)->uid, -1);
if (res == -1) {
int errno_save = errno;
syscall(OURSYS_setresgid, -1, old->egid, -1);
return errno_save;
}
return 0;
}
/* Regain Privileges */
static void lo_restore_cred(struct lo_cred *old)
{
int res;
res = syscall(OURSYS_setresuid, -1, old->euid, -1);
if (res == -1) {
fuse_log(FUSE_LOG_ERR, "seteuid(%u): %m\n", old->euid);
exit(1);
}
res = syscall(OURSYS_setresgid, -1, old->egid, -1);
if (res == -1) {
fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid);
exit(1);
}
}
static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
const char *name, mode_t mode, dev_t rdev,
const char *link)
{
int res;
int saverr;
struct lo_inode *dir;
struct fuse_entry_param e;
struct lo_cred old = {};
if (!is_safe_path_component(name)) {
fuse_reply_err(req, EINVAL);
return;
}
dir = lo_inode(req, parent);
if (!dir) {
fuse_reply_err(req, EBADF);
return;
}
saverr = ENOMEM;
saverr = lo_change_cred(req, &old);
if (saverr) {
goto out;
}
res = mknod_wrapper(dir->fd, name, link, mode, rdev);
saverr = errno;
lo_restore_cred(&old);
if (res == -1) {
goto out;
}
saverr = lo_do_lookup(req, parent, name, &e);
if (saverr) {
goto out;
}
fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent,
name, (unsigned long long)e.ino);
fuse_reply_entry(req, &e);
return;
out:
fuse_reply_err(req, saverr);
}
static void lo_mknod(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode, dev_t rdev)
{
lo_mknod_symlink(req, parent, name, mode, rdev, NULL);
}
static void lo_mkdir(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode)
{
lo_mknod_symlink(req, parent, name, S_IFDIR | mode, 0, NULL);
}
static void lo_symlink(fuse_req_t req, const char *link, fuse_ino_t parent,
const char *name)
{
lo_mknod_symlink(req, parent, name, S_IFLNK, 0, link);
}
static int linkat_empty_nofollow(struct lo_data *lo, struct lo_inode *inode,
int dfd, const char *name)
{
int res;
struct lo_inode *parent;
char path[PATH_MAX];
if (inode->is_symlink) {
res = linkat(inode->fd, "", dfd, name, AT_EMPTY_PATH);
if (res == -1 && (errno == ENOENT || errno == EINVAL)) {
/* Sorry, no race free way to hard-link a symlink. */
if (lo->norace) {
errno = EPERM;
} else {
goto fallback;
}
}
return res;
}
sprintf(path, "%i", inode->fd);
return linkat(lo->proc_self_fd, path, dfd, name, AT_SYMLINK_FOLLOW);
fallback:
res = lo_parent_and_name(lo, inode, path, &parent);
if (res != -1) {
res = linkat(parent->fd, path, dfd, name, 0);
unref_inode_lolocked(lo, parent, 1);
}
return res;
}
static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent,
const char *name)
{
int res;
struct lo_data *lo = lo_data(req);
struct lo_inode *inode;
struct fuse_entry_param e;
int saverr;
if (!is_safe_path_component(name)) {
fuse_reply_err(req, EINVAL);
return;
}
inode = lo_inode(req, ino);
if (!inode) {
fuse_reply_err(req, EBADF);
return;
}
memset(&e, 0, sizeof(struct fuse_entry_param));
e.attr_timeout = lo->timeout;
e.entry_timeout = lo->timeout;
res = linkat_empty_nofollow(lo, inode, lo_fd(req, parent), name);
if (res == -1) {
goto out_err;
}
res = fstatat(inode->fd, "", &e.attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
if (res == -1) {
goto out_err;
}
pthread_mutex_lock(&lo->mutex);
inode->refcount++;
pthread_mutex_unlock(&lo->mutex);
e.ino = inode->fuse_ino;
fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent,
name, (unsigned long long)e.ino);
fuse_reply_entry(req, &e);
return;
out_err:
saverr = errno;
fuse_reply_err(req, saverr);
}
static void lo_rmdir(fuse_req_t req, fuse_ino_t parent, const char *name)
{
int res;
if (!is_safe_path_component(name)) {
fuse_reply_err(req, EINVAL);
return;
}
res = unlinkat(lo_fd(req, parent), name, AT_REMOVEDIR);
fuse_reply_err(req, res == -1 ? errno : 0);
}
static void lo_rename(fuse_req_t req, fuse_ino_t parent, const char *name,
fuse_ino_t newparent, const char *newname,
unsigned int flags)
{
int res;
if (!is_safe_path_component(name) || !is_safe_path_component(newname)) {
fuse_reply_err(req, EINVAL);
return;
}
if (flags) {
#ifndef SYS_renameat2
fuse_reply_err(req, EINVAL);
#else
res = syscall(SYS_renameat2, lo_fd(req, parent), name,
lo_fd(req, newparent), newname, flags);
if (res == -1 && errno == ENOSYS) {
fuse_reply_err(req, EINVAL);
} else {
fuse_reply_err(req, res == -1 ? errno : 0);
}
#endif
return;
}
res = renameat(lo_fd(req, parent), name, lo_fd(req, newparent), newname);
fuse_reply_err(req, res == -1 ? errno : 0);
}
static void lo_unlink(fuse_req_t req, fuse_ino_t parent, const char *name)
{
int res;
if (!is_safe_path_component(name)) {
fuse_reply_err(req, EINVAL);
return;
}
res = unlinkat(lo_fd(req, parent), name, 0);
fuse_reply_err(req, res == -1 ? errno : 0);
}
static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode,
uint64_t n)
{
if (!inode) {
return;
}
pthread_mutex_lock(&lo->mutex);
assert(inode->refcount >= n);
inode->refcount -= n;
if (!inode->refcount) {
struct lo_inode *prev, *next;
prev = inode->prev;
next = inode->next;
next->prev = prev;
prev->next = next;
lo_map_remove(&lo->ino_map, inode->fuse_ino);
pthread_mutex_unlock(&lo->mutex);
close(inode->fd);
free(inode);
} else {
pthread_mutex_unlock(&lo->mutex);
}
}
static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup)
{
struct lo_data *lo = lo_data(req);
struct lo_inode *inode;
inode = lo_inode(req, ino);
if (!inode) {
return;
}
fuse_log(FUSE_LOG_DEBUG, " forget %lli %lli -%lli\n",
(unsigned long long)ino, (unsigned long long)inode->refcount,
(unsigned long long)nlookup);
unref_inode_lolocked(lo, inode, nlookup);
}
static void lo_forget(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup)
{
lo_forget_one(req, ino, nlookup);
fuse_reply_none(req);
}
static void lo_forget_multi(fuse_req_t req, size_t count,
struct fuse_forget_data *forgets)
{
int i;
for (i = 0; i < count; i++) {
lo_forget_one(req, forgets[i].ino, forgets[i].nlookup);
}
fuse_reply_none(req);
}
static void lo_readlink(fuse_req_t req, fuse_ino_t ino)
{
char buf[PATH_MAX + 1];
int res;
res = readlinkat(lo_fd(req, ino), "", buf, sizeof(buf));
if (res == -1) {
return (void)fuse_reply_err(req, errno);
}
if (res == sizeof(buf)) {
return (void)fuse_reply_err(req, ENAMETOOLONG);
}
buf[res] = '\0';
fuse_reply_readlink(req, buf);
}
struct lo_dirp {
DIR *dp;
struct dirent *entry;
off_t offset;
};
static struct lo_dirp *lo_dirp(fuse_req_t req, struct fuse_file_info *fi)
{
struct lo_data *lo = lo_data(req);
struct lo_map_elem *elem;
pthread_mutex_lock(&lo->mutex);
elem = lo_map_get(&lo->dirp_map, fi->fh);
pthread_mutex_unlock(&lo->mutex);
if (!elem) {
return NULL;
}
return elem->dirp;
}
static void lo_opendir(fuse_req_t req, fuse_ino_t ino,
struct fuse_file_info *fi)
{
int error = ENOMEM;
struct lo_data *lo = lo_data(req);
struct lo_dirp *d;
int fd;
ssize_t fh;
d = calloc(1, sizeof(struct lo_dirp));
if (d == NULL) {
goto out_err;
}
fd = openat(lo_fd(req, ino), ".", O_RDONLY);
if (fd == -1) {
goto out_errno;
}
d->dp = fdopendir(fd);
if (d->dp == NULL) {
goto out_errno;
}
d->offset = 0;
d->entry = NULL;
pthread_mutex_lock(&lo->mutex);
fh = lo_add_dirp_mapping(req, d);
pthread_mutex_unlock(&lo->mutex);
if (fh == -1) {
goto out_err;
}
fi->fh = fh;
if (lo->cache == CACHE_ALWAYS) {
fi->keep_cache = 1;
}
fuse_reply_open(req, fi);
return;
out_errno:
error = errno;
out_err:
if (d) {
if (d->dp) {
closedir(d->dp);
}
if (fd != -1) {
close(fd);
}
free(d);
}
fuse_reply_err(req, error);
}
static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
off_t offset, struct fuse_file_info *fi, int plus)
{
struct lo_data *lo = lo_data(req);
struct lo_dirp *d;
struct lo_inode *dinode;
char *buf = NULL;
char *p;
size_t rem = size;
int err = EBADF;
dinode = lo_inode(req, ino);
if (!dinode) {
goto error;
}
d = lo_dirp(req, fi);
if (!d) {
goto error;
}
err = ENOMEM;
buf = calloc(1, size);
if (!buf) {
goto error;
}
p = buf;
if (offset != d->offset) {
seekdir(d->dp, offset);
d->entry = NULL;
d->offset = offset;
}
while (1) {
size_t entsize;
off_t nextoff;
const char *name;
if (!d->entry) {
errno = 0;
d->entry = readdir(d->dp);
if (!d->entry) {
if (errno) { /* Error */
err = errno;
goto error;
} else { /* End of stream */
break;
}
}
}
nextoff = d->entry->d_off;
name = d->entry->d_name;
fuse_ino_t entry_ino = 0;
struct fuse_entry_param e = (struct fuse_entry_param){
.attr.st_ino = d->entry->d_ino,
.attr.st_mode = d->entry->d_type << 12,
};
/* Hide root's parent directory */
if (dinode == &lo->root && strcmp(name, "..") == 0) {
e.attr.st_ino = lo->root.ino;
e.attr.st_mode = DT_DIR << 12;
}
if (plus) {
if (!is_dot_or_dotdot(name)) {
err = lo_do_lookup(req, ino, name, &e);
if (err) {
goto error;
}
entry_ino = e.ino;
}
entsize = fuse_add_direntry_plus(req, p, rem, name, &e, nextoff);
} else {
entsize = fuse_add_direntry(req, p, rem, name, &e.attr, nextoff);
}
if (entsize > rem) {
if (entry_ino != 0) {
lo_forget_one(req, entry_ino, 1);
}
break;
}
p += entsize;
rem -= entsize;
d->entry = NULL;
d->offset = nextoff;
}
err = 0;
error:
/*
* If there's an error, we can only signal it if we haven't stored
* any entries yet - otherwise we'd end up with wrong lookup
* counts for the entries that are already in the buffer. So we
* return what we've collected until that point.
*/
if (err && rem == size) {
fuse_reply_err(req, err);
} else {
fuse_reply_buf(req, buf, size - rem);
}
free(buf);
}
static void lo_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
off_t offset, struct fuse_file_info *fi)
{
lo_do_readdir(req, ino, size, offset, fi, 0);
}
static void lo_readdirplus(fuse_req_t req, fuse_ino_t ino, size_t size,
off_t offset, struct fuse_file_info *fi)
{
lo_do_readdir(req, ino, size, offset, fi, 1);
}
static void lo_releasedir(fuse_req_t req, fuse_ino_t ino,
struct fuse_file_info *fi)
{
struct lo_data *lo = lo_data(req);
struct lo_dirp *d;
(void)ino;
d = lo_dirp(req, fi);
if (!d) {
fuse_reply_err(req, EBADF);
return;
}
pthread_mutex_lock(&lo->mutex);
lo_map_remove(&lo->dirp_map, fi->fh);
pthread_mutex_unlock(&lo->mutex);
closedir(d->dp);
free(d);
fuse_reply_err(req, 0);
}
static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode, struct fuse_file_info *fi)
{
int fd;
struct lo_data *lo = lo_data(req);
struct fuse_entry_param e;
int err;
struct lo_cred old = {};
fuse_log(FUSE_LOG_DEBUG, "lo_create(parent=%" PRIu64 ", name=%s)\n", parent,
name);
if (!is_safe_path_component(name)) {
fuse_reply_err(req, EINVAL);
return;
}
err = lo_change_cred(req, &old);
if (err) {
goto out;
}
fd = openat(lo_fd(req, parent), name, (fi->flags | O_CREAT) & ~O_NOFOLLOW,
mode);
err = fd == -1 ? errno : 0;
lo_restore_cred(&old);
if (!err) {
ssize_t fh;
pthread_mutex_lock(&lo->mutex);
fh = lo_add_fd_mapping(req, fd);
pthread_mutex_unlock(&lo->mutex);
if (fh == -1) {
close(fd);
fuse_reply_err(req, ENOMEM);
return;
}
fi->fh = fh;
err = lo_do_lookup(req, parent, name, &e);
}
if (lo->cache == CACHE_NEVER) {
fi->direct_io = 1;
} else if (lo->cache == CACHE_ALWAYS) {
fi->keep_cache = 1;
}
out:
if (err) {
fuse_reply_err(req, err);
} else {
fuse_reply_create(req, &e, fi);
}
}
static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync,
struct fuse_file_info *fi)
{
int res;
struct lo_dirp *d;
int fd;
(void)ino;
d = lo_dirp(req, fi);
if (!d) {
fuse_reply_err(req, EBADF);
return;
}
fd = dirfd(d->dp);
if (datasync) {
res = fdatasync(fd);
} else {
res = fsync(fd);
}
fuse_reply_err(req, res == -1 ? errno : 0);
}
static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
{
int fd;
ssize_t fh;
char buf[64];
struct lo_data *lo = lo_data(req);
fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=%" PRIu64 ", flags=%d)\n", ino,
fi->flags);
/*
* With writeback cache, kernel may send read requests even
* when userspace opened write-only
*/
if (lo->writeback && (fi->flags & O_ACCMODE) == O_WRONLY) {
fi->flags &= ~O_ACCMODE;
fi->flags |= O_RDWR;
}
/*
* With writeback cache, O_APPEND is handled by the kernel.
* This breaks atomicity (since the file may change in the
* underlying filesystem, so that the kernel's idea of the
* end of the file isn't accurate anymore). In this example,
* we just accept that. A more rigorous filesystem may want
* to return an error here
*/
if (lo->writeback && (fi->flags & O_APPEND)) {
fi->flags &= ~O_APPEND;
}
sprintf(buf, "%i", lo_fd(req, ino));
fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
if (fd == -1) {
return (void)fuse_reply_err(req, errno);
}
pthread_mutex_lock(&lo->mutex);
fh = lo_add_fd_mapping(req, fd);
pthread_mutex_unlock(&lo->mutex);
if (fh == -1) {
close(fd);
fuse_reply_err(req, ENOMEM);
return;
}
fi->fh = fh;
if (lo->cache == CACHE_NEVER) {
fi->direct_io = 1;
} else if (lo->cache == CACHE_ALWAYS) {
fi->keep_cache = 1;
}
fuse_reply_open(req, fi);
}
static void lo_release(fuse_req_t req, fuse_ino_t ino,
struct fuse_file_info *fi)
{
struct lo_data *lo = lo_data(req);
int fd;
(void)ino;
fd = lo_fi_fd(req, fi);
pthread_mutex_lock(&lo->mutex);
lo_map_remove(&lo->fd_map, fi->fh);
pthread_mutex_unlock(&lo->mutex);
close(fd);
fuse_reply_err(req, 0);
}
static void lo_flush(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
{
int res;
(void)ino;
res = close(dup(lo_fi_fd(req, fi)));
fuse_reply_err(req, res == -1 ? errno : 0);
}
static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
struct fuse_file_info *fi)
{
int res;
int fd;
char *buf;
fuse_log(FUSE_LOG_DEBUG, "lo_fsync(ino=%" PRIu64 ", fi=0x%p)\n", ino,
(void *)fi);
if (!fi) {
struct lo_data *lo = lo_data(req);
res = asprintf(&buf, "%i", lo_fd(req, ino));
if (res == -1) {
return (void)fuse_reply_err(req, errno);
}
fd = openat(lo->proc_self_fd, buf, O_RDWR);
free(buf);
if (fd == -1) {
return (void)fuse_reply_err(req, errno);
}
} else {
fd = lo_fi_fd(req, fi);
}
if (datasync) {
res = fdatasync(fd);
} else {
res = fsync(fd);
}
if (!fi) {
close(fd);
}
fuse_reply_err(req, res == -1 ? errno : 0);
}
static void lo_read(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset,
struct fuse_file_info *fi)
{
struct fuse_bufvec buf = FUSE_BUFVEC_INIT(size);
fuse_log(FUSE_LOG_DEBUG,
"lo_read(ino=%" PRIu64 ", size=%zd, "
"off=%lu)\n",
ino, size, (unsigned long)offset);
buf.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK;
buf.buf[0].fd = lo_fi_fd(req, fi);
buf.buf[0].pos = offset;
fuse_reply_data(req, &buf);
}
static void lo_write_buf(fuse_req_t req, fuse_ino_t ino,
struct fuse_bufvec *in_buf, off_t off,
struct fuse_file_info *fi)
{
(void)ino;
ssize_t res;
struct fuse_bufvec out_buf = FUSE_BUFVEC_INIT(fuse_buf_size(in_buf));
bool cap_fsetid_dropped = false;
out_buf.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK;
out_buf.buf[0].fd = lo_fi_fd(req, fi);
out_buf.buf[0].pos = off;
fuse_log(FUSE_LOG_DEBUG,
"lo_write_buf(ino=%" PRIu64 ", size=%zd, off=%lu)\n", ino,
out_buf.buf[0].size, (unsigned long)off);
/*
* If kill_priv is set, drop CAP_FSETID which should lead to kernel
* clearing setuid/setgid on file.
*/
if (fi->kill_priv) {
res = drop_effective_cap("FSETID", &cap_fsetid_dropped);
if (res != 0) {
fuse_reply_err(req, res);
return;
}
}
res = fuse_buf_copy(&out_buf, in_buf);
if (res < 0) {
fuse_reply_err(req, -res);
} else {
fuse_reply_write(req, (size_t)res);
}
if (cap_fsetid_dropped) {
res = gain_effective_cap("FSETID");
if (res) {
fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_FSETID\n");
}
}
}
static void lo_statfs(fuse_req_t req, fuse_ino_t ino)
{
int res;
struct statvfs stbuf;
res = fstatvfs(lo_fd(req, ino), &stbuf);
if (res == -1) {
fuse_reply_err(req, errno);
} else {
fuse_reply_statfs(req, &stbuf);
}
}
static void lo_fallocate(fuse_req_t req, fuse_ino_t ino, int mode, off_t offset,
off_t length, struct fuse_file_info *fi)
{
int err = EOPNOTSUPP;
(void)ino;
#ifdef CONFIG_FALLOCATE
err = fallocate(lo_fi_fd(req, fi), mode, offset, length);
if (err < 0) {
err = errno;
}
#elif defined(CONFIG_POSIX_FALLOCATE)
if (mode) {
fuse_reply_err(req, EOPNOTSUPP);
return;
}
err = posix_fallocate(lo_fi_fd(req, fi), offset, length);
#endif
fuse_reply_err(req, err);
}
static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
int op)
{
int res;
(void)ino;
res = flock(lo_fi_fd(req, fi), op);
fuse_reply_err(req, res == -1 ? errno : 0);
}
static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
size_t size)
{
struct lo_data *lo = lo_data(req);
char *value = NULL;
char procname[64];
struct lo_inode *inode;
ssize_t ret;
int saverr;
int fd = -1;
inode = lo_inode(req, ino);
if (!inode) {
fuse_reply_err(req, EBADF);
return;
}
saverr = ENOSYS;
if (!lo_data(req)->xattr) {
goto out;
}
fuse_log(FUSE_LOG_DEBUG, "lo_getxattr(ino=%" PRIu64 ", name=%s size=%zd)\n",
ino, name, size);
if (inode->is_symlink) {
/* Sorry, no race free way to getxattr on symlink. */
saverr = EPERM;
goto out;
}
sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
goto out_err;
}
if (size) {
value = malloc(size);
if (!value) {
goto out_err;
}
ret = fgetxattr(fd, name, value, size);
if (ret == -1) {
goto out_err;
}
saverr = 0;
if (ret == 0) {
goto out;
}
fuse_reply_buf(req, value, ret);
} else {
ret = fgetxattr(fd, name, NULL, 0);
if (ret == -1) {
goto out_err;
}
fuse_reply_xattr(req, ret);
}
out_free:
free(value);
if (fd >= 0) {
close(fd);
}
return;
out_err:
saverr = errno;
out:
fuse_reply_err(req, saverr);
goto out_free;
}
static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
{
struct lo_data *lo = lo_data(req);
char *value = NULL;
char procname[64];
struct lo_inode *inode;
ssize_t ret;
int saverr;
int fd = -1;
inode = lo_inode(req, ino);
if (!inode) {
fuse_reply_err(req, EBADF);
return;
}
saverr = ENOSYS;
if (!lo_data(req)->xattr) {
goto out;
}
fuse_log(FUSE_LOG_DEBUG, "lo_listxattr(ino=%" PRIu64 ", size=%zd)\n", ino,
size);
if (inode->is_symlink) {
/* Sorry, no race free way to listxattr on symlink. */
saverr = EPERM;
goto out;
}
sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
goto out_err;
}
if (size) {
value = malloc(size);
if (!value) {
goto out_err;
}
ret = flistxattr(fd, value, size);
if (ret == -1) {
goto out_err;
}
saverr = 0;
if (ret == 0) {
goto out;
}
fuse_reply_buf(req, value, ret);
} else {
ret = flistxattr(fd, NULL, 0);
if (ret == -1) {
goto out_err;
}
fuse_reply_xattr(req, ret);
}
out_free:
free(value);
if (fd >= 0) {
close(fd);
}
return;
out_err:
saverr = errno;
out:
fuse_reply_err(req, saverr);
goto out_free;
}
static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
const char *value, size_t size, int flags)
{
char procname[64];
struct lo_data *lo = lo_data(req);
struct lo_inode *inode;
ssize_t ret;
int saverr;
int fd = -1;
inode = lo_inode(req, ino);
if (!inode) {
fuse_reply_err(req, EBADF);
return;
}
saverr = ENOSYS;
if (!lo_data(req)->xattr) {
goto out;
}
fuse_log(FUSE_LOG_DEBUG, "lo_setxattr(ino=%" PRIu64
", name=%s value=%s size=%zd)\n", ino, name, value, size);
if (inode->is_symlink) {
/* Sorry, no race free way to setxattr on symlink. */
saverr = EPERM;
goto out;
}
sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDWR);
if (fd < 0) {
saverr = errno;
goto out;
}
ret = fsetxattr(fd, name, value, size, flags);
saverr = ret == -1 ? errno : 0;
out:
if (fd >= 0) {
close(fd);
}
fuse_reply_err(req, saverr);
}
static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name)
{
char procname[64];
struct lo_data *lo = lo_data(req);
struct lo_inode *inode;
ssize_t ret;
int saverr;
int fd = -1;
inode = lo_inode(req, ino);
if (!inode) {
fuse_reply_err(req, EBADF);
return;
}
saverr = ENOSYS;
if (!lo_data(req)->xattr) {
goto out;
}
fuse_log(FUSE_LOG_DEBUG, "lo_removexattr(ino=%" PRIu64 ", name=%s)\n", ino,
name);
if (inode->is_symlink) {
/* Sorry, no race free way to setxattr on symlink. */
saverr = EPERM;
goto out;
}
sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDWR);
if (fd < 0) {
saverr = errno;
goto out;
}
ret = fremovexattr(fd, name);
saverr = ret == -1 ? errno : 0;
out:
if (fd >= 0) {
close(fd);
}
fuse_reply_err(req, saverr);
}
#ifdef HAVE_COPY_FILE_RANGE
static void lo_copy_file_range(fuse_req_t req, fuse_ino_t ino_in, off_t off_in,
struct fuse_file_info *fi_in, fuse_ino_t ino_out,
off_t off_out, struct fuse_file_info *fi_out,
size_t len, int flags)
{
int in_fd, out_fd;
ssize_t res;
in_fd = lo_fi_fd(req, fi_in);
out_fd = lo_fi_fd(req, fi_out);
fuse_log(FUSE_LOG_DEBUG,
"lo_copy_file_range(ino=%" PRIu64 "/fd=%d, "
"off=%lu, ino=%" PRIu64 "/fd=%d, "
"off=%lu, size=%zd, flags=0x%x)\n",
ino_in, in_fd, off_in, ino_out, out_fd, off_out, len, flags);
res = copy_file_range(in_fd, &off_in, out_fd, &off_out, len, flags);
if (res < 0) {
fuse_reply_err(req, -errno);
} else {
fuse_reply_write(req, res);
}
}
#endif
static void lo_lseek(fuse_req_t req, fuse_ino_t ino, off_t off, int whence,
struct fuse_file_info *fi)
{
off_t res;
(void)ino;
res = lseek(lo_fi_fd(req, fi), off, whence);
if (res != -1) {
fuse_reply_lseek(req, res);
} else {
fuse_reply_err(req, errno);
}
}
static struct fuse_lowlevel_ops lo_oper = {
.init = lo_init,
.lookup = lo_lookup,
.mkdir = lo_mkdir,
.mknod = lo_mknod,
.symlink = lo_symlink,
.link = lo_link,
.unlink = lo_unlink,
.rmdir = lo_rmdir,
.rename = lo_rename,
.forget = lo_forget,
.forget_multi = lo_forget_multi,
.getattr = lo_getattr,
.setattr = lo_setattr,
.readlink = lo_readlink,
.opendir = lo_opendir,
.readdir = lo_readdir,
.readdirplus = lo_readdirplus,
.releasedir = lo_releasedir,
.fsyncdir = lo_fsyncdir,
.create = lo_create,
.open = lo_open,
.release = lo_release,
.flush = lo_flush,
.fsync = lo_fsync,
.read = lo_read,
.write_buf = lo_write_buf,
.statfs = lo_statfs,
.fallocate = lo_fallocate,
.flock = lo_flock,
.getxattr = lo_getxattr,
.listxattr = lo_listxattr,
.setxattr = lo_setxattr,
.removexattr = lo_removexattr,
#ifdef HAVE_COPY_FILE_RANGE
.copy_file_range = lo_copy_file_range,
#endif
.lseek = lo_lseek,
};
/* Print vhost-user.json backend program capabilities */
static void print_capabilities(void)
{
printf("{\n");
printf(" \"type\": \"fs\"\n");
printf("}\n");
}
/*
* Move to a new mount, net, and pid namespaces to isolate this process.
*/
static void setup_namespaces(struct lo_data *lo, struct fuse_session *se)
{
pid_t child;
/*
* Create a new pid namespace for *child* processes. We'll have to
* fork in order to enter the new pid namespace. A new mount namespace
* is also needed so that we can remount /proc for the new pid
* namespace.
*
* Our UNIX domain sockets have been created. Now we can move to
* an empty network namespace to prevent TCP/IP and other network
* activity in case this process is compromised.
*/
if (unshare(CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWNET) != 0) {
fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWPID | CLONE_NEWNS): %m\n");
exit(1);
}
child = fork();
if (child < 0) {
fuse_log(FUSE_LOG_ERR, "fork() failed: %m\n");
exit(1);
}
if (child > 0) {
pid_t waited;
int wstatus;
/* The parent waits for the child */
do {
waited = waitpid(child, &wstatus, 0);
} while (waited < 0 && errno == EINTR && !se->exited);
/* We were terminated by a signal, see fuse_signals.c */
if (se->exited) {
exit(0);
}
if (WIFEXITED(wstatus)) {
exit(WEXITSTATUS(wstatus));
}
exit(1);
}
/* Send us SIGTERM when the parent thread terminates, see prctl(2) */
prctl(PR_SET_PDEATHSIG, SIGTERM);
/*
* If the mounts have shared propagation then we want to opt out so our
* mount changes don't affect the parent mount namespace.
*/
if (mount(NULL, "/", NULL, MS_REC | MS_SLAVE, NULL) < 0) {
fuse_log(FUSE_LOG_ERR, "mount(/, MS_REC|MS_SLAVE): %m\n");
exit(1);
}
/* The child must remount /proc to use the new pid namespace */
if (mount("proc", "/proc", "proc",
MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) {
fuse_log(FUSE_LOG_ERR, "mount(/proc): %m\n");
exit(1);
}
/* Now we can get our /proc/self/fd directory file descriptor */
lo->proc_self_fd = open("/proc/self/fd", O_PATH);
if (lo->proc_self_fd == -1) {
fuse_log(FUSE_LOG_ERR, "open(/proc/self/fd, O_PATH): %m\n");
exit(1);
}
}
/*
* Capture the capability state, we'll need to restore this for individual
* threads later; see load_capng.
*/
static void setup_capng(void)
{
/* Note this accesses /proc so has to happen before the sandbox */
if (capng_get_caps_process()) {
fuse_log(FUSE_LOG_ERR, "capng_get_caps_process\n");
exit(1);
}
pthread_mutex_init(&cap.mutex, NULL);
pthread_mutex_lock(&cap.mutex);
cap.saved = capng_save_state();
if (!cap.saved) {
fuse_log(FUSE_LOG_ERR, "capng_save_state\n");
exit(1);
}
pthread_mutex_unlock(&cap.mutex);
}
static void cleanup_capng(void)
{
free(cap.saved);
cap.saved = NULL;
pthread_mutex_destroy(&cap.mutex);
}
/*
* Make the source directory our root so symlinks cannot escape and no other
* files are accessible. Assumes unshare(CLONE_NEWNS) was already called.
*/
static void setup_mounts(const char *source)
{
int oldroot;
int newroot;
if (mount(source, source, NULL, MS_BIND, NULL) < 0) {
fuse_log(FUSE_LOG_ERR, "mount(%s, %s, MS_BIND): %m\n", source, source);
exit(1);
}
/* This magic is based on lxc's lxc_pivot_root() */
oldroot = open("/", O_DIRECTORY | O_RDONLY | O_CLOEXEC);
if (oldroot < 0) {
fuse_log(FUSE_LOG_ERR, "open(/): %m\n");
exit(1);
}
newroot = open(source, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
if (newroot < 0) {
fuse_log(FUSE_LOG_ERR, "open(%s): %m\n", source);
exit(1);
}
if (fchdir(newroot) < 0) {
fuse_log(FUSE_LOG_ERR, "fchdir(newroot): %m\n");
exit(1);
}
if (syscall(__NR_pivot_root, ".", ".") < 0) {
fuse_log(FUSE_LOG_ERR, "pivot_root(., .): %m\n");
exit(1);
}
if (fchdir(oldroot) < 0) {
fuse_log(FUSE_LOG_ERR, "fchdir(oldroot): %m\n");
exit(1);
}
if (mount("", ".", "", MS_SLAVE | MS_REC, NULL) < 0) {
fuse_log(FUSE_LOG_ERR, "mount(., MS_SLAVE | MS_REC): %m\n");
exit(1);
}
if (umount2(".", MNT_DETACH) < 0) {
fuse_log(FUSE_LOG_ERR, "umount2(., MNT_DETACH): %m\n");
exit(1);
}
if (fchdir(newroot) < 0) {
fuse_log(FUSE_LOG_ERR, "fchdir(newroot): %m\n");
exit(1);
}
close(newroot);
close(oldroot);
}
/*
* Lock down this process to prevent access to other processes or files outside
* source directory. This reduces the impact of arbitrary code execution bugs.
*/
static void setup_sandbox(struct lo_data *lo, struct fuse_session *se,
bool enable_syslog)
{
setup_namespaces(lo, se);
setup_mounts(lo->source);
setup_seccomp(enable_syslog);
}
/* Raise the maximum number of open file descriptors */
static void setup_nofile_rlimit(void)
{
const rlim_t max_fds = 1000000;
struct rlimit rlim;
if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) {
fuse_log(FUSE_LOG_ERR, "getrlimit(RLIMIT_NOFILE): %m\n");
exit(1);
}
if (rlim.rlim_cur >= max_fds) {
return; /* nothing to do */
}
rlim.rlim_cur = max_fds;
rlim.rlim_max = max_fds;
if (setrlimit(RLIMIT_NOFILE, &rlim) < 0) {
/* Ignore SELinux denials */
if (errno == EPERM) {
return;
}
fuse_log(FUSE_LOG_ERR, "setrlimit(RLIMIT_NOFILE): %m\n");
exit(1);
}
}
static void log_func(enum fuse_log_level level, const char *fmt, va_list ap)
{
g_autofree char *localfmt = NULL;
if (current_log_level < level) {
return;
}
if (current_log_level == FUSE_LOG_DEBUG) {
if (!use_syslog) {
localfmt = g_strdup_printf("[%" PRId64 "] [ID: %08ld] %s",
get_clock(), syscall(__NR_gettid), fmt);
} else {
localfmt = g_strdup_printf("[ID: %08ld] %s", syscall(__NR_gettid),
fmt);
}
fmt = localfmt;
}
if (use_syslog) {
int priority = LOG_ERR;
switch (level) {
case FUSE_LOG_EMERG:
priority = LOG_EMERG;
break;
case FUSE_LOG_ALERT:
priority = LOG_ALERT;
break;
case FUSE_LOG_CRIT:
priority = LOG_CRIT;
break;
case FUSE_LOG_ERR:
priority = LOG_ERR;
break;
case FUSE_LOG_WARNING:
priority = LOG_WARNING;
break;
case FUSE_LOG_NOTICE:
priority = LOG_NOTICE;
break;
case FUSE_LOG_INFO:
priority = LOG_INFO;
break;
case FUSE_LOG_DEBUG:
priority = LOG_DEBUG;
break;
}
vsyslog(priority, fmt, ap);
} else {
vfprintf(stderr, fmt, ap);
}
}
int main(int argc, char *argv[])
{
struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
struct fuse_session *se;
struct fuse_cmdline_opts opts;
struct lo_data lo = {
.debug = 0,
.writeback = 0,
.proc_self_fd = -1,
};
struct lo_map_elem *root_elem;
int ret = -1;
/* Don't mask creation mode, kernel already did that */
umask(0);
pthread_mutex_init(&lo.mutex, NULL);
lo.root.next = lo.root.prev = &lo.root;
lo.root.fd = -1;
lo.root.fuse_ino = FUSE_ROOT_ID;
lo.cache = CACHE_NORMAL;
/*
* Set up the ino map like this:
* [0] Reserved (will not be used)
* [1] Root inode
*/
lo_map_init(&lo.ino_map);
lo_map_reserve(&lo.ino_map, 0)->in_use = false;
root_elem = lo_map_reserve(&lo.ino_map, lo.root.fuse_ino);
root_elem->inode = &lo.root;
lo_map_init(&lo.dirp_map);
lo_map_init(&lo.fd_map);
if (fuse_parse_cmdline(&args, &opts) != 0) {
return 1;
}
fuse_set_log_func(log_func);
use_syslog = opts.syslog;
if (use_syslog) {
openlog("virtiofsd", LOG_PID, LOG_DAEMON);
}
if (opts.show_help) {
printf("usage: %s [options]\n\n", argv[0]);
fuse_cmdline_help();
printf(" -o source=PATH shared directory tree\n");
fuse_lowlevel_help();
ret = 0;
goto err_out1;
} else if (opts.show_version) {
fuse_lowlevel_version();
ret = 0;
goto err_out1;
} else if (opts.print_capabilities) {
print_capabilities();
ret = 0;
goto err_out1;
}
if (fuse_opt_parse(&args, &lo, lo_opts, NULL) == -1) {
return 1;
}
/*
* log_level is 0 if not configured via cmd options (0 is LOG_EMERG,
* and we don't use this log level).
*/
if (opts.log_level != 0) {
current_log_level = opts.log_level;
}
lo.debug = opts.debug;
if (lo.debug) {
current_log_level = FUSE_LOG_DEBUG;
}
lo.root.refcount = 2;
if (lo.source) {
struct stat stat;
int res;
res = lstat(lo.source, &stat);
if (res == -1) {
fuse_log(FUSE_LOG_ERR, "failed to stat source (\"%s\"): %m\n",
lo.source);
exit(1);
}
if (!S_ISDIR(stat.st_mode)) {
fuse_log(FUSE_LOG_ERR, "source is not a directory\n");
exit(1);
}
} else {
lo.source = "/";
}
lo.root.is_symlink = false;
if (!lo.timeout_set) {
switch (lo.cache) {
case CACHE_NEVER:
lo.timeout = 0.0;
break;
case CACHE_NORMAL:
lo.timeout = 1.0;
break;
case CACHE_ALWAYS:
lo.timeout = 86400.0;
break;
}
} else if (lo.timeout < 0) {
fuse_log(FUSE_LOG_ERR, "timeout is negative (%lf)\n", lo.timeout);
exit(1);
}
lo.root.fd = open(lo.source, O_PATH);
if (lo.root.fd == -1) {
fuse_log(FUSE_LOG_ERR, "open(\"%s\", O_PATH): %m\n", lo.source);
exit(1);
}
se = fuse_session_new(&args, &lo_oper, sizeof(lo_oper), &lo);
if (se == NULL) {
goto err_out1;
}
if (fuse_set_signal_handlers(se) != 0) {
goto err_out2;
}
if (fuse_session_mount(se) != 0) {
goto err_out3;
}
fuse_daemonize(opts.foreground);
setup_nofile_rlimit();
/* Must be before sandbox since it wants /proc */
setup_capng();
setup_sandbox(&lo, se, opts.syslog);
/* Block until ctrl+c or fusermount -u */
ret = virtio_loop(se);
fuse_session_unmount(se);
cleanup_capng();
err_out3:
fuse_remove_signal_handlers(se);
err_out2:
fuse_session_destroy(se);
err_out1:
fuse_opt_free_args(&args);
lo_map_destroy(&lo.fd_map);
lo_map_destroy(&lo.dirp_map);
lo_map_destroy(&lo.ino_map);
if (lo.proc_self_fd >= 0) {
close(lo.proc_self_fd);
}
if (lo.root.fd >= 0) {
close(lo.root.fd);
}
return ret ? 1 : 0;
}
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