On 02/11/2015 16:18, Cole Robinson wrote:
>> > - if ((access(un.sun_path, F_OK) == 0) &&
>> > - unlink(un.sun_path) < 0) {
>> > + if (unlink(un.sun_path) < 0) {
>> > error_setg_errno(errp, errno,
>> > "Failed to unlink socket %s", un.sun_path);
>> > goto err;
>> >
> This is a serious semantic change, after this patch you will get:
>
> $ ./x86_64-softmmu/qemu-system-x86_64 -vnc unix:/tmp/idontexist.sock
> qemu-system-x86_64: -vnc unix:/tmp/idontexist.sock: Failed to start VNC
> server: Failed to unlink socket /tmp/idontexist.sock: No such file or
> directory
>
> Previously it would 'just work'. Common libvirt usage depends on this as well
>
> Yeah there's a TOCTTOU race here, but it's very minor: if sun_path is created
> after the access() check, qemu is just going to fail to start since bind()
> will barf if the unix socket path exists.
You're right. I misread how to test the change.
The right change is what Markus proposed.
Paolo
