Re: requesting stable backport for 4.1 and 4.4: 95a762e2c8c9 ("bpf: fix incorrect sign extension in check_alu_op()")

Greg Kroah-Hartman
2018-03-18T12:57:06Z

On Sat, Mar 17, 2018 at 07:17:17PM -0700, Jann Horn wrote:
> Hi!
>
> Someone on Twitter
> (https://twitter.com/vnik5287/status/974277953394651137) is pointing
> out that the BPF fix commit 95a762e2c8c942780948091f8f2a4f32fce1ac6f
> ("bpf: fix incorrect sign extension in check_alu_op()") needs to be
> applied all the way back to 4.4, and probably also 4.1; my "Fixes:"
> tag on that commit is incorrect. I assumed that without map access,
> math correctness issues don't matter, but actually, this one does
> matter because check_cond_jmp_op() will omit verification for branches
> that appear to be unreachable (comparison of CONST_IMM register and a
> constant value). :/

Ok, but the patch doesn't apply cleanly to 4.4.y, and I don't know the
bpf code well enough to do it myself. Can you provide a working
backport so that I can queue it up?

thanks,

greg k-h