Hi
On Tue, Aug 17, 2021 at 12:56 PM Michal Privoznik <mpriv...@redhat.com>
wrote:
> When opening a path that starts with "/dev/fdset/" the control
> jumps into qemu_parse_fdset() and then into
> monitor_fdset_dup_fd_add(). In here, corresponding fdset is found
> and then all FDs from the set are iterated over trying to find an
> FD that matches expected access mode. For instance, if caller
> wants O_WRONLY then the FD set has to contain an O_WRONLY FD.
>
> If no such FD is found then errno is set to EACCES which results
> in very misleading error messages, for instance:
>
> Could not dup FD for /dev/fdset/3 flags 441: Permission denied
>
> There is no permission issue, the problem is that there was no FD
> within given fdset that was in expected access mode. Therefore,
> let's set errno to EBADFD, which gives us somewhat better
> error messages:
>
> Could not dup FD for /dev/fdset/3 flags 441: File descriptor in bad state
>
> Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
>
I am not sure this is any better. If you try to open a read-only file, the
system also reports EACCES (Permission denied). This is what the current
code models, I believe.
> ---
> monitor/misc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/monitor/misc.c b/monitor/misc.c
> index ffe7966870..a0eda0d574 100644
> --- a/monitor/misc.c
> +++ b/monitor/misc.c
> @@ -1347,7 +1347,7 @@ int monitor_fdset_dup_fd_add(int64_t fdset_id, int
> flags)
> }
>
> if (fd == -1) {
> - errno = EACCES;
> + errno = EBADFD;
> return -1;
> }
>
> --
> 2.31.1
>
>
