On 8/17/21 11:59 AM, Marc-André Lureau wrote: > 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.
Fair enough. Another idea I had was that if an FD that's O_RDWR was passed but only read or only write access was requested then such FD could be accepted because it is capable of reading/writing. But since patch 1/2 was accepted then I guess 2/2 is not that much needed. Michal
