On Mon, Oct 12, 2009 at 3:03 PM, KOSAKI Motohiro <[email protected]> wrote: > Hi > > Sorry for the delaying. > >> On Sat, Oct 10, 2009 at 2:32 AM, KOSAKI Motohiro >> <[email protected]> wrote: >> >> >> It does seem like a maximum spin count should be put in there - and >> >> maybe a timeout as well (since with FUSE etc it's possible to engineer >> >> page faults that take arbitrarily long). >> >> Also, it occurs to me that: >> > >> > makes sense. >> > I like maximum spin rather than timeout. >> >> I'm worried about the scenario where process A sets its cmdline buffer >> to point to a page which will take a _VERY_ long time to pagein (maybe >> forever), and then process B goes to try to read its cmdline. What >> happens now? > > Honestly, I don't worry about so much. if attacker want DoS attack, fork bomb > is > efficient than this way. then, attacker never use this.
Fork bombs and etc can be mitigated by resource limits; but if the command line is placed on a page that will take a very long time to fault, then that cannot be mitigated... But again, this DoS already exists and isn't any easier with this patch, so I think it's a separate issue. >> Process A can arrange for this to happen by using a FUSE filesystem >> that sits on a read forever. And since the first thing the admin's >> likely to do to track down the problem is 'ps awux', this is liable to >> be a rather nasty DoS... > > Probably, I haven't understand this paragraph. Why is this FUSE related issue? Just an example of how one can create a page that will take a very long time to fault in. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
