[Virtio-fs] [virtiofsd PATCH v6 1/6] virtiofsd: add .ioctl() support

[Vivek Goyal]

On Mon, Oct 11, 2021 at 11:09:33AM +0800, Jeffle Xu wrote:
> For passthrough, it passes corresponding ioctls to host directly.
> 
> Currently only these ioctls that handling persistent inode flags, i.e.,
> FS_IOC_[G|S]ETFLAGS and FS_IOC_FS[G|S]ETXATTR are supported for security
> concern, though it's implemented in a quite general way, so that we can
> expand the scope of allowed ioctls if it is really needed later.
> 
> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
> ---
>  tools/virtiofsd/passthrough_ll.c      | 59 +++++++++++++++++++++++++++
>  tools/virtiofsd/passthrough_seccomp.c |  1 +
>  2 files changed, 60 insertions(+)
> 
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index b76d878509..5969d67810 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -47,6 +47,7 @@
>  #include <dirent.h>
>  #include <pthread.h>
>  #include <sys/file.h>
> +#include <sys/ioctl.h>
>  #include <sys/mount.h>
>  #include <sys/prctl.h>
>  #include <sys/resource.h>
> @@ -54,6 +55,7 @@
>  #include <sys/wait.h>
>  #include <sys/xattr.h>
>  #include <syslog.h>
> +#include <linux/fs.h>
>  
>  #include "qemu/cutils.h"
>  #include "passthrough_helpers.h"
> @@ -2105,6 +2107,62 @@ out:
>      fuse_reply_err(req, saverr);
>  }
>  
> +
> +static void lo_ioctl(fuse_req_t req, fuse_ino_t ino, unsigned int cmd, void *arg,
> +                          struct fuse_file_info *fi, unsigned flags, const void *in_buf,
> +                          size_t in_bufsz, size_t out_bufsz)
> +{
> +    int fd = lo_fi_fd(req, fi);
> +    int res;
> +    int saverr = ENOSYS;
> +    int dir;
> +    void *buf = NULL;
> +    size_t size = 0;
> +
> +    fuse_log(FUSE_LOG_DEBUG, "lo_ioctl(ino=%" PRIu64 ", cmd=0x%x, flags=0x%x, "
> +            "in_bufsz = %lu, out_bufsz = %lu)\n",
> +            ino, cmd, flags, in_bufsz, out_bufsz);
> +
> +    if (cmd != FS_IOC_SETFLAGS || cmd != FS_IOC_GETFLAGS ||
> +        cmd != FS_IOC_FSSETXATTR || cmd != FS_IOC_FSGETXATTR)
> +        goto out;
> +
> +    /* unrestricted ioctl is not supported yet */
> +    if (flags & FUSE_IOCTL_UNRESTRICTED)
> +        goto out;
> +
> +    dir = _IOC_DIR(cmd);
> +
> +    if (dir & _IOC_READ) {
> +        size = out_bufsz;
> +        buf = malloc(size);
> +        if (!buf)
> +            goto out_err;
> +
> +        if (dir & _IOC_WRITE)
> +            memcpy(buf, in_buf, size);
> +
> +        res = ioctl(fd, cmd, buf);
> +    }
> +    else if (dir & _IOC_WRITE) {

Typically else is on same line as } braces.

} else if (dir & _IOC_WRITE) {

Have you tried running qemu/script/checkpatch.pl on these patches. Does it
flag it?

Vivek

> +        res = ioctl(fd, cmd, in_buf);
> +    }
> +    else {
> +        res = ioctl(fd, cmd, arg);
> +    }
> +
> +    if (res < 0)
> +        goto out_err;
> +
> +    fuse_reply_ioctl(req, 0, buf, size);
> +    return;
> +
> +out_err:
> +    saverr = errno;
> +out:
> +    fuse_reply_err(req, saverr);
> +}
> +
>  static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync,
>                          struct fuse_file_info *fi)
>  {
> @@ -3278,6 +3336,7 @@ static struct fuse_lowlevel_ops lo_oper = {
>      .fsyncdir = lo_fsyncdir,
>      .create = lo_create,
>      .getlk = lo_getlk,
> +    .ioctl = lo_ioctl,
>      .setlk = lo_setlk,
>      .open = lo_open,
>      .release = lo_release,
> diff --git a/tools/virtiofsd/passthrough_seccomp.c b/tools/virtiofsd/passthrough_seccomp.c
> index 62441cfcdb..2a5f7614fc 100644
> --- a/tools/virtiofsd/passthrough_seccomp.c
> +++ b/tools/virtiofsd/passthrough_seccomp.c
> @@ -62,6 +62,7 @@ static const int syscall_allowlist[] = {
>      SCMP_SYS(gettid),
>      SCMP_SYS(gettimeofday),
>      SCMP_SYS(getxattr),
> +    SCMP_SYS(ioctl),
>      SCMP_SYS(linkat),
>      SCMP_SYS(listxattr),
>      SCMP_SYS(lseek),
> -- 
> 2.27.0
>