* Philippe Mathieu-Daudé (phi...@redhat.com) wrote:
> On 12/12/19 5:38 PM, Dr. David Alan Gilbert (git) wrote:
> > From: Stefan Hajnoczi <stefa...@redhat.com>
> >
> > 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 <stefa...@redhat.com>
> > ---
> > tools/virtiofsd/passthrough_ll.c | 129 ++++++++++++++++++++++++-------
> > 1 file changed, 102 insertions(+), 27 deletions(-)
> >
> > diff --git a/tools/virtiofsd/passthrough_ll.c
> > b/tools/virtiofsd/passthrough_ll.c
> > index 123f095990..006908f25a 100644
> > --- a/tools/virtiofsd/passthrough_ll.c
> > +++ b/tools/virtiofsd/passthrough_ll.c
> > @@ -110,6 +110,9 @@ struct lo_data {
> > 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[] = {
> > @@ -379,9 +382,9 @@ static int lo_parent_and_name(struct lo_data *lo,
> > struct lo_inode *inode,
> > int res;
> > 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) {
> > fuse_log(FUSE_LOG_WARNING, "lo_parent_and_name: readlink failed:
> > %m\n");
> > goto fail_noretry;
> > @@ -477,9 +480,9 @@ static int utimensat_empty(struct lo_data *lo, struct
> > lo_inode *inode,
> > }
> > 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:
> > 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) {
> > res = fchmod(fd, attr->st_mode);
> > } else {
> > - sprintf(procname, "/proc/self/fd/%i", ifd);
> > - res = chmod(procname, attr->st_mode);
> > + sprintf(procname, "%i", ifd);
> > + res = fchmodat(lo->proc_self_fd, procname, attr->st_mode, 0);
> > }
> > if (res == -1) {
> > 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) {
> > + int truncfd;
> > +
> > if (fi) {
> > - res = ftruncate(fd, attr->st_size);
> > + truncfd = fd;
> > } else {
> > - sprintf(procname, "/proc/self/fd/%i", ifd);
> > - res = truncate(procname, attr->st_size);
> > + 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;
> > @@ -857,9 +872,9 @@ static int linkat_empty_nofollow(struct lo_data *lo,
> > struct lo_inode *inode,
> > 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:
> > res = lo_parent_and_name(lo, inode, path, &parent);
> > @@ -1387,8 +1402,8 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino,
> > struct fuse_file_info *fi)
> > fi->flags &= ~O_APPEND;
> > }
> > - sprintf(buf, "/proc/self/fd/%i", lo_fd(req, ino));
> > - fd = open(buf, fi->flags & ~O_NOFOLLOW);
> > + 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);
> > }
> > @@ -1440,8 +1455,8 @@ static void lo_flush(fuse_req_t req, fuse_ino_t ino,
> > struct fuse_file_info *fi)
> > static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
> > struct fuse_file_info *fi)
> > {
> > + struct lo_data *lo = lo_data(req);
>
> We can initialize this one ...
>
> > int res;
> > - (void)ino;
> > int fd;
> > char *buf;
> > @@ -1449,12 +1464,12 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t
> > ino, int datasync,
> > (void *)fi);
> > if (!fi) {
>
> ... here:
>
> lo = lo_data(req);
>
> Similarly in other functions, but I see this is the style used by this file.
I moved that one, I'll keep my out for others; it's nice to keep the
scope small.
> > - res = asprintf(&buf, "/proc/self/fd/%i", lo_fd(req, ino));
> > + res = asprintf(&buf, "%i", lo_fd(req, ino));
> > if (res == -1) {
> > return (void)fuse_reply_err(req, errno);
> > }
> > - fd = open(buf, O_RDWR);
> > + fd = openat(lo->proc_self_fd, buf, O_RDWR);
> > free(buf);
> > if (fd == -1) {
> > return (void)fuse_reply_err(req, errno);
> > @@ -1570,11 +1585,13 @@ 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,
> > 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) {
> > @@ -1599,7 +1616,11 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t
> > ino, const char *name,
> > 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) {
> > value = malloc(size);
> > @@ -1607,7 +1628,7 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t
> > ino, const char *name,
> > goto out_err;
> > }
> > - ret = getxattr(procname, name, value, size);
> > + ret = fgetxattr(fd, name, value, size);
> > if (ret == -1) {
> > goto out_err;
> > }
> > @@ -1618,7 +1639,7 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t
> > ino, const char *name,
> > fuse_reply_buf(req, value, ret);
> > } else {
> > - ret = getxattr(procname, name, NULL, 0);
> > + ret = fgetxattr(fd, name, NULL, 0);
> > if (ret == -1) {
> > goto out_err;
> > }
> > @@ -1627,6 +1648,10 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t
> > ino, const char *name,
> > }
> > out_free:
> > free(value);
> > +
> > + if (fd >= 0) {
> > + close(fd);
> > + }
> > return;
> > out_err:
> > @@ -1638,11 +1663,13 @@ out:
> > 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) {
> > @@ -1666,7 +1693,11 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t
> > ino, size_t size)
> > 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) {
> > value = malloc(size);
> > @@ -1674,7 +1705,7 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t
> > ino, size_t size)
> > goto out_err;
> > }
> > - ret = listxattr(procname, value, size);
> > + ret = flistxattr(fd, value, size);
> > if (ret == -1) {
> > goto out_err;
> > }
> > @@ -1685,7 +1716,7 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t
> > ino, size_t size)
> > fuse_reply_buf(req, value, ret);
> > } else {
> > - ret = listxattr(procname, NULL, 0);
> > + ret = flistxattr(fd, NULL, 0);
> > if (ret == -1) {
> > goto out_err;
> > }
> > @@ -1694,6 +1725,10 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t
> > ino, size_t size)
> > }
> > out_free:
> > free(value);
> > +
> > + if (fd >= 0) {
> > + close(fd);
> > + }
> > return;
> > out_err:
> > @@ -1707,9 +1742,11 @@ 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) {
> > @@ -1734,21 +1771,31 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t
> > ino, const char *name,
> > 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;
> > 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) {
> > @@ -1772,12 +1819,20 @@ static void lo_removexattr(fuse_req_t req,
> > fuse_ino_t ino, const char *name)
> > 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;
> > out:
> > + if (fd >= 0) {
> > + close(fd);
> > + }
> > fuse_reply_err(req, saverr);
> > }
> > @@ -1870,12 +1925,25 @@ static void print_capabilities(void)
> > 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[])
> > {
> > 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 };
> > + struct lo_data lo = {
> > + .debug = 0,
> > + .writeback = 0,
> > + .proc_self_fd = -1,
> > + };
> > struct lo_map_elem *root_elem;
> > int ret = -1;
> > @@ -1986,6 +2054,9 @@ int main(int argc, char *argv[])
> > 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 */
> > ret = virtio_loop(se);
> > @@ -2001,6 +2072,10 @@ err_out1:
> > 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);
> > }
> >
>
> Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
Thanks!
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
