Messages in this thread | | | Date | Wed, 20 Jul 2022 23:36:08 +0200 | From | Peter Zijlstra <> | Subject | Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation |
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On Wed, Jul 20, 2022 at 12:36:38PM -0700, Kees Cook wrote: > On Wed, Jul 20, 2022 at 11:07:26AM -0700, Linus Torvalds wrote: > > On Wed, Jul 20, 2022 at 10:50 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > [ 2.464117] missing return thunk: lkdtm_rodata_do_nothing+0x0/0x8-lkdtm_rodata_do_nothing+0x5/0x8: e9 00 00 00 00 > > > > Well, that looks like a "jmp" instruction that has never been relocated. > > Peter, Josh, and I drilled down into this recently[1] and discussed > some solutions[2]. > > This test is doing what's expected: it needed an arch-agnostic way to do > a "return", and when the way to do that changed, it also changed (which > would normally be good, but in this case broke it). It's been happily > being used as part of the per-section architectural behavior testing[3] > of execution-vs-expected-memory-permissions for quite a long while now. > > I'd rather not remove it (or do it dynamically) since the point is to > test what has been generated by the toolchain/build process and stuffed > into the .rodata section. i.e. making sure gadgets there can't be > executed, that the boot-time section permission-setting works correctly, > etc. Before the retbleed mitigation, this test worked for all > architectures; I'd hate to regress it. :( > > -Kees > > [1] https://lore.kernel.org/lkml/Ys66hwtFcGbYmoiZ@hirez.programming.kicks-ass.net/ > [2] https://lore.kernel.org/lkml/20220713213133.455599-1-keescook@chromium.org/ > [3] e.g. https://linux.kernelci.org/test/plan/id/62d61ee8ef31e0f0faa39bff/
Josh posted this:
https://lkml.kernel.org/r/8ec0039712f252693049c70ed3891d39a2357112.1658155446.git.jpoimboe@kernel.org
which I picked up today; barring robot fail I'll push it to x86/urgent tomorrow.
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