On 7/21/26 12:05, Alyssa Ross wrote: > Demi Marie Obenour writes: > >> On 7/15/26 14:54, Alyssa Ross wrote: >>> Demi Marie Obenour writes: >>> >>>> On 7/13/26 05:04, Alyssa Ross wrote: >>>>> Demi Marie Obenour writes: >>>>> >>>>>> This seems to be a fairly significant hole in the VMM's sandbox. >>>>>> Various code operates in that directory and isn't secure against >>>>>> symlink attacks. >>>>>> >>>>>> Does the VMM really need write access to that directory? Could it >>>>>> be given access to a subdirectory that is mounted "nosymfollow"? >>>>> >>>>> I think it's just so it can create e.g. the serial file. That could >>>>> indeed be moved to a subdirectory. The ideal solution is of course for >>>>> Cloud Hypervisor to be able to accept every file it would otherwise >>>>> create as an open file descriptor, which I expect will happen >>>>> eventually. >>>> >>>> Should it be moved to a subdirectory for now? That would make the >>>> sandbox meaningful in practice. >>> >>> I suppose it could be. Might make more sense to dedicate efforts >>> towards fixing Cloud Hypervisor to accept file descriptors for the ~2 >>> paths it currently needs to create, though. (That's obviously more >>> work, but also more useful.) If we were to work around this in >>> Spectrum, we could keep symlinks outside the directory pointing into it, >>> to keep paths nice and avoid churn once we can put them back in the >>> parent directory. >> >> Do you happen to know which paths these are? > > I think it might just be "serial"? Not sure. How difficult would it be to modify Cloud Hypervisor so this is passed as a file descriptor? -- Sincerely, Demi Marie Obenour (she/her/hers)