Re: [PATCH v7 1/7] virtiofsd: Fix fuse setxattr() API change issue

[Dr. David Alan Gilbert]

* Vivek Goyal (vgoyal@redhat.com) wrote:
> With kernel header updates fuse_setxattr_in struct has grown in size.
> But this new struct size only takes affect if user has opted in
> for fuse feature FUSE_SETXATTR_EXT otherwise fuse continues to
> send "fuse_setxattr_in" of older size. Older size is determined
> by FUSE_COMPAT_SETXATTR_IN_SIZE.
> 
> Fix this. If we have not opted in for FUSE_SETXATTR_EXT, then
> expect that we will get fuse_setxattr_in of size FUSE_COMPAT_SETXATTR_IN_SIZE
> and not sizeof(struct fuse_sexattr_in).
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Yeh it's a bit of a grim fix, but I think it's the best we can do, and
we need to get it in since the headers have already been merged.
(I don't think libfuse has a fix for this in yet itself, but it might
survive because it doesn't bother copying the data like we do with
mbuf).


Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  tools/virtiofsd/fuse_common.h   | 5 +++++
>  tools/virtiofsd/fuse_lowlevel.c | 7 ++++++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/virtiofsd/fuse_common.h b/tools/virtiofsd/fuse_common.h
> index fa9671872e..0c2665b977 100644
> --- a/tools/virtiofsd/fuse_common.h
> +++ b/tools/virtiofsd/fuse_common.h
> @@ -372,6 +372,11 @@ struct fuse_file_info {
>   */
>  #define FUSE_CAP_HANDLE_KILLPRIV_V2 (1 << 28)
>  
> +/**
> + * Indicates that file server supports extended struct fuse_setxattr_in
> + */
> +#define FUSE_CAP_SETXATTR_EXT (1 << 29)
> +
>  /**
>   * Ioctl flags
>   *
> diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c
> index 7fe2cef1eb..c2b6ff1686 100644
> --- a/tools/virtiofsd/fuse_lowlevel.c
> +++ b/tools/virtiofsd/fuse_lowlevel.c
> @@ -1419,8 +1419,13 @@ static void do_setxattr(fuse_req_t req, fuse_ino_t 
> nodeid,
>      struct fuse_setxattr_in *arg;
>      const char *name;
>      const char *value;
> +    bool setxattr_ext = req->se->conn.want & FUSE_CAP_SETXATTR_EXT;
>  
> -    arg = fuse_mbuf_iter_advance(iter, sizeof(*arg));
> +    if (setxattr_ext) {
> +        arg = fuse_mbuf_iter_advance(iter, sizeof(*arg));
> +    } else {
> +        arg = fuse_mbuf_iter_advance(iter, FUSE_COMPAT_SETXATTR_IN_SIZE);
> +    }
>      name = fuse_mbuf_iter_advance_str(iter);
>      if (!arg || !name) {
>          fuse_reply_err(req, EINVAL);
> -- 
> 2.25.4
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK