Messages in this thread | | | Date | Wed, 24 Nov 2010 21:33:00 +0300 | From | Vasiliy Kulikov <> | Subject | Re: [PATCH v2] gpu: vga: limit kmalloc'ed memory size |
| |
Andrew,
On Tue, Nov 23, 2010 at 12:46 -0800, Andrew Morton wrote: > What I'm suggesting is that we simply do > > kbuf = strndup_user(buf, count); > > and make strndup_user() do the right thing if `count' turned out to be > crazy large. THis way we don't have to sprinkle decisions about "crazy > largeness" all over the kernel. > > And the way in which I suggest that strndup_user() decides whether the > length is too great is to try to kmalloc that amount of memory. > If it succeeds then fine, proceed.
I don't think that it is a good idea - the process would have an ability to allocate too much system memory bypassing any limits. Assuming that the kernel would only double the memory is not right - even if the process is limited in physical memory it may pass address of e.g. mapped file.
Also this specific driver is happy with very low limit of copied string.
> If it fails then return an error, > probably ENOMEM.
It is already done in strndup_user().
> And that attempt to invoke kmalloc() shouldn't spew a > warning.
It is not obvious for me to change strndup_user's behaviour, I'm not familiar with this code.
-- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments
| |