On Mon, Jan 21, 2019 at 08:05:10AM +1300, Tycho Andersen wrote: > Hey Luc, > > On Fri, Dec 21, 2018 at 11:47:19PM +0100, Luc Van Oostenryck wrote: > > On Thu, Dec 20, 2018 at 12:59:27PM -0700, Tycho Andersen wrote: > > > Hi all, > > > > > > A while ago I talked with various people about whether some static > > > analsys of copy_to_user() could be productive in finding infoleaks. > > > Unfortunately, due to the various issues outlined in the patch notes, it > > > doesn't seem like it is. Perhaps these checks are useful to put in just > > > to future proof ourselves against these sorts of issues, though. > > > > > > Anyway, here's the code. Thoughts welcome! > > > > Hi, > > > > I'm taking the first patch directly but I won't be able to look > > closer at the other patches until next week. > > Any chance you can take a peek at these? Hi, Sorry, I've had few available time the last weeks. I had look at them shortly after you send them but I haven't yet made my mind about them. I'm quite reluctant to add complexity (the AST walking) if it doesn't bring much benefit if any. In, short the problems are: 1) duplication of the AST walking 2) unreliable type because of using void * 3) unreliable size because array to pointer degeneracy There is some solutions, though: 1) what *could* be done is to add a method 'check' to struct symbol_op and call it, *for example*, just after op->expand() in expand_symbol_call() (and add a mechanism to set this method for the symbol corresponding to copy_to_user()). Otherwise, splitting the AST walking from sparse.c and making it something generic would be preferable. Another approach could be keep the check via OP_CALL but doing it just after linearization, before the optimization destroy the types (and add, if needed, some flag to force linearize_cast() keep absolutely all type info). 2) this one seems pretty hopeless 3) the current calls degenerate()/create_pointer() do indeed destroy the original type and (at first sight) no 'addressof' should exist anymore after evaluation. This is inconsistent with the existence of expand_addressof(). By changing degenerate()/create_pointer() the original type should stay available. Sorry again for the late reply, -- Luc
