On Tue, Jul 28, 2020 at 10:07 AM David Laight <David.Laight@xxxxxxxxxx> wrote: > > From: Christoph Hellwig > > Sent: 27 July 2020 17:24 > > > > On Mon, Jul 27, 2020 at 06:16:32PM +0200, Jason A. Donenfeld wrote: > > > Maybe sockptr_advance should have some safety checks and sometimes > > > return -EFAULT? Or you should always use the implementation where > > > being a kernel address is an explicit bit of sockptr_t, rather than > > > being implicit? > > > > I already have a patch to use access_ok to check the whole range in > > init_user_sockptr. > > That doesn't make (much) difference to the code paths that ignore > the user-supplied length. > OTOH doing the user/kernel check on the base address (not an > incremented one) means that the correct copy function is always > selected. Right, I had the same reaction in reading this, but actually, his code gets rid of the sockptr_advance stuff entirely and never mutates, so even though my point about attacking those pointers was missed, the code does the better thing now -- checking the base address and never mutating the pointer. So I think we're good. > > Perhaps the functions should all be passed a 'const sockptr_t'. > The typedef could be made 'const' - requiring non-const items > explicitly use the union/struct itself. I was thinking the same, but just by making the pointers inside the struct const. However, making the whole struct const via the typedef is a much better idea. That'd probably require changing the signature of init_user_sockptr a bit, which would be fine, but indeed I think this would be a very positive change. Jason
