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virtiofsd: use /proc/self/fd/ O_PATH file descriptor

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Sandboxing will remove /proc from the mount namespace so we can no
longer build string paths into "/proc/self/fd/...".

Keep an O_PATH file descriptor so we can still re-open fds via
/proc/self/fd.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2019-03-12 15:48:50 +00:00 committed by Dr. David Alan Gilbert
parent 752272da2b
commit 9f59d175e2
1 changed files with 103 additions and 27 deletions
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130
tools/virtiofsd/passthrough_ll.c
View File

@ -110,6 +110,9 @@ struct lo_data {
struct lo_map ino_map; /* 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 dirp_map; /* protected by lo->mutex */
struct lo_map fd_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[] = { static const struct fuse_opt lo_opts[] = {
@ -379,9 +382,9 @@ static int lo_parent_and_name(struct lo_data *lo, struct lo_inode *inode,
int res; int res;
retry: retry:
sprintf(procname, "/proc/self/fd/%i", inode->fd); sprintf(procname, "%i", inode->fd);
res = readlink(procname, path, PATH_MAX); res = readlinkat(lo->proc_self_fd, procname, path, PATH_MAX);
if (res < 0) { if (res < 0) {
fuse_log(FUSE_LOG_WARNING, "%s: readlink failed: %m\n", __func__); fuse_log(FUSE_LOG_WARNING, "%s: readlink failed: %m\n", __func__);
goto fail_noretry; goto fail_noretry;
@ -477,9 +480,9 @@ static int utimensat_empty(struct lo_data *lo, struct lo_inode *inode,
} }
return res; return res;
} }
sprintf(path, "/proc/self/fd/%i", inode->fd); sprintf(path, "%i", inode->fd);
return utimensat(AT_FDCWD, path, tv, 0); return utimensat(lo->proc_self_fd, path, tv, 0);
fallback: fallback:
res = lo_parent_and_name(lo, inode, path, &parent); res = lo_parent_and_name(lo, inode, path, &parent);
@ -535,8 +538,8 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
if (fi) { if (fi) {
res = fchmod(fd, attr->st_mode); res = fchmod(fd, attr->st_mode);
} else { } else {
sprintf(procname, "/proc/self/fd/%i", ifd); sprintf(procname, "%i", ifd);
res = chmod(procname, attr->st_mode); res = fchmodat(lo->proc_self_fd, procname, attr->st_mode, 0);
} }
if (res == -1) { if (res == -1) {
goto out_err; goto out_err;
@ -552,11 +555,23 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
} }
} }
if (valid & FUSE_SET_ATTR_SIZE) { if (valid & FUSE_SET_ATTR_SIZE) {
int truncfd;
if (fi) { if (fi) {
res = ftruncate(fd, attr->st_size); truncfd = fd;
} else { } else {
sprintf(procname, "/proc/self/fd/%i", ifd); sprintf(procname, "%i", ifd);
res = truncate(procname, attr->st_size); 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) { if (res == -1) {
goto out_err; goto out_err;
@ -874,9 +889,9 @@ static int linkat_empty_nofollow(struct lo_data *lo, struct lo_inode *inode,
return res; return res;
} }
sprintf(path, "/proc/self/fd/%i", inode->fd); sprintf(path, "%i", inode->fd);
return linkat(AT_FDCWD, path, dfd, name, AT_SYMLINK_FOLLOW); return linkat(lo->proc_self_fd, path, dfd, name, AT_SYMLINK_FOLLOW);
fallback: fallback:
res = lo_parent_and_name(lo, inode, path, &parent); res = lo_parent_and_name(lo, inode, path, &parent);
@ -1404,8 +1419,8 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
fi->flags &= ~O_APPEND; fi->flags &= ~O_APPEND;
} }
sprintf(buf, "/proc/self/fd/%i", lo_fd(req, ino)); sprintf(buf, "%i", lo_fd(req, ino));
fd = open(buf, fi->flags & ~O_NOFOLLOW); fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
if (fd == -1) { if (fd == -1) {
return (void)fuse_reply_err(req, errno); return (void)fuse_reply_err(req, errno);
} }
@ -1458,7 +1473,6 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
struct fuse_file_info *fi) struct fuse_file_info *fi)
{ {
int res; int res;
(void)ino;
int fd; int fd;
char *buf; char *buf;
@ -1466,12 +1480,14 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
(void *)fi); (void *)fi);
if (!fi) { if (!fi) {
res = asprintf(&buf, "/proc/self/fd/%i", lo_fd(req, ino)); struct lo_data *lo = lo_data(req);
res = asprintf(&buf, "%i", lo_fd(req, ino));
if (res == -1) { if (res == -1) {
return (void)fuse_reply_err(req, errno); return (void)fuse_reply_err(req, errno);
} }
fd = open(buf, O_RDWR); fd = openat(lo->proc_self_fd, buf, O_RDWR);
free(buf); free(buf);
if (fd == -1) { if (fd == -1) {
return (void)fuse_reply_err(req, errno); return (void)fuse_reply_err(req, errno);
@ -1587,11 +1603,13 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name, static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
size_t size) size_t size)
{ {
struct lo_data *lo = lo_data(req);
char *value = NULL; char *value = NULL;
char procname[64]; char procname[64];
struct lo_inode *inode; struct lo_inode *inode;
ssize_t ret; ssize_t ret;
int saverr; int saverr;
int fd = -1;
inode = lo_inode(req, ino); inode = lo_inode(req, ino);
if (!inode) { if (!inode) {
@ -1616,7 +1634,11 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
goto out; goto out;
} }
sprintf(procname, "/proc/self/fd/%i", inode->fd); sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
goto out_err;
}
if (size) { if (size) {
value = malloc(size); value = malloc(size);
@ -1624,7 +1646,7 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
goto out_err; goto out_err;
} }
ret = getxattr(procname, name, value, size); ret = fgetxattr(fd, name, value, size);
if (ret == -1) { if (ret == -1) {
goto out_err; goto out_err;
} }
@ -1635,7 +1657,7 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
fuse_reply_buf(req, value, ret); fuse_reply_buf(req, value, ret);
} else { } else {
ret = getxattr(procname, name, NULL, 0); ret = fgetxattr(fd, name, NULL, 0);
if (ret == -1) { if (ret == -1) {
goto out_err; goto out_err;
} }
@ -1644,6 +1666,10 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
} }
out_free: out_free:
free(value); free(value);
if (fd >= 0) {
close(fd);
}
return; return;
out_err: out_err:
@ -1655,11 +1681,13 @@ out:
static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) 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 *value = NULL;
char procname[64]; char procname[64];
struct lo_inode *inode; struct lo_inode *inode;
ssize_t ret; ssize_t ret;
int saverr; int saverr;
int fd = -1;
inode = lo_inode(req, ino); inode = lo_inode(req, ino);
if (!inode) { if (!inode) {
@ -1683,7 +1711,11 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
goto out; goto out;
} }
sprintf(procname, "/proc/self/fd/%i", inode->fd); sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
goto out_err;
}
if (size) { if (size) {
value = malloc(size); value = malloc(size);
@ -1691,7 +1723,7 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
goto out_err; goto out_err;
} }
ret = listxattr(procname, value, size); ret = flistxattr(fd, value, size);
if (ret == -1) { if (ret == -1) {
goto out_err; goto out_err;
} }
@ -1702,7 +1734,7 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
fuse_reply_buf(req, value, ret); fuse_reply_buf(req, value, ret);
} else { } else {
ret = listxattr(procname, NULL, 0); ret = flistxattr(fd, NULL, 0);
if (ret == -1) { if (ret == -1) {
goto out_err; goto out_err;
} }
@ -1711,6 +1743,10 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
} }
out_free: out_free:
free(value); free(value);
if (fd >= 0) {
close(fd);
}
return; return;
out_err: out_err:
@ -1724,9 +1760,11 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
const char *value, size_t size, int flags) const char *value, size_t size, int flags)
{ {
char procname[64]; char procname[64];
struct lo_data *lo = lo_data(req);
struct lo_inode *inode; struct lo_inode *inode;
ssize_t ret; ssize_t ret;
int saverr; int saverr;
int fd = -1;
inode = lo_inode(req, ino); inode = lo_inode(req, ino);
if (!inode) { if (!inode) {
@ -1751,21 +1789,31 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
goto out; goto out;
} }
sprintf(procname, "/proc/self/fd/%i", inode->fd); sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDWR);
if (fd < 0) {
saverr = errno;
goto out;
}
ret = setxattr(procname, name, value, size, flags); ret = fsetxattr(fd, name, value, size, flags);
saverr = ret == -1 ? errno : 0; saverr = ret == -1 ? errno : 0;
out: out:
if (fd >= 0) {
close(fd);
}
fuse_reply_err(req, saverr); fuse_reply_err(req, saverr);
} }
static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name) static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name)
{ {
char procname[64]; char procname[64];
struct lo_data *lo = lo_data(req);
struct lo_inode *inode; struct lo_inode *inode;
ssize_t ret; ssize_t ret;
int saverr; int saverr;
int fd = -1;
inode = lo_inode(req, ino); inode = lo_inode(req, ino);
if (!inode) { if (!inode) {
@ -1789,12 +1837,20 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name)
goto out; goto out;
} }
sprintf(procname, "/proc/self/fd/%i", inode->fd); sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDWR);
if (fd < 0) {
saverr = errno;
goto out;
}
ret = removexattr(procname, name); ret = fremovexattr(fd, name);
saverr = ret == -1 ? errno : 0; saverr = ret == -1 ? errno : 0;
out: out:
if (fd >= 0) {
close(fd);
}
fuse_reply_err(req, saverr); fuse_reply_err(req, saverr);
} }
@ -1887,12 +1943,25 @@ static void print_capabilities(void)
printf("}\n"); printf("}\n");
} }
static void setup_proc_self_fd(struct lo_data *lo)
{
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);
}
}
int main(int argc, char *argv[]) int main(int argc, char *argv[])
{ {
struct fuse_args args = FUSE_ARGS_INIT(argc, argv); struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
struct fuse_session *se; struct fuse_session *se;
struct fuse_cmdline_opts opts; struct fuse_cmdline_opts opts;
struct lo_data lo = { .debug = 0, .writeback = 0 }; struct lo_data lo = {
.debug = 0,
.writeback = 0,
.proc_self_fd = -1,
};
struct lo_map_elem *root_elem; struct lo_map_elem *root_elem;
int ret = -1; int ret = -1;
@ -2003,6 +2072,9 @@ int main(int argc, char *argv[])
fuse_daemonize(opts.foreground); fuse_daemonize(opts.foreground);
/* Must be after daemonize to get the right /proc/self/fd */
setup_proc_self_fd(&lo);
/* Block until ctrl+c or fusermount -u */ /* Block until ctrl+c or fusermount -u */
ret = virtio_loop(se); ret = virtio_loop(se);
@ -2018,6 +2090,10 @@ err_out1:
lo_map_destroy(&lo.dirp_map); lo_map_destroy(&lo.dirp_map);
lo_map_destroy(&lo.ino_map); lo_map_destroy(&lo.ino_map);
if (lo.proc_self_fd >= 0) {
close(lo.proc_self_fd);
}
if (lo.root.fd >= 0) { if (lo.root.fd >= 0) {
close(lo.root.fd); close(lo.root.fd);
} }