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SubjectRe: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode
On Tue, May 9, 2017 at 9:03 AM, Christoph Hellwig <> wrote:
> On Tue, May 09, 2017 at 06:02:50AM -0700, Christoph Hellwig wrote:
>> On Tue, May 09, 2017 at 06:00:01AM -0700, Andy Lutomirski wrote:
>> > fs/splice.c has some, ahem, interesting uses that have been the source
>> > of nasty exploits in the past. Converting them to use iov_iter
>> > properly would be really, really nice. Christoph, I don't suppose
>> > you'd like to do that?
>> I can take care of all the fs code including this one.
> I spent the afternoon hacking up where I'd like this to head. It's
> completely untested as of now:

Ooooh yes! Nice work.

I love this:
but I wonder what it'll cause out-of-tree code to do. I mean, I'd
rather nothing out-of-tree be calling these, but I'd hate 3rd party
hacks even more.
This accidentally(?) removes the kernel-doc comments.
Could this be made defensive? (Return 0 if ret wraps, for example?) I
see what the comment says, but not everyone will read that. :(
Perhaps unconditionally set USER_DS on exit instead of retaining
whatever was there?


Kees Cook
Pixel Security

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