Messages in this thread | | | Date | Thu, 23 Apr 2020 11:06:14 -0700 | From | Kees Cook <> | Subject | Re: linux-next: Tree for Apr 22 (objtool warnings) |
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On Wed, Apr 22, 2020 at 11:44:06AM -0500, Josh Poimboeuf wrote: > On Wed, Apr 22, 2020 at 08:35:29AM -0700, Randy Dunlap wrote: > > On 4/22/20 12:10 AM, Stephen Rothwell wrote: > > > Hi all, > > > > > > Changes since 20200421: > > > > > > > on x86_64: > > In both cases the unreachable instruction happens immediately after a > call to a function which is truncated with a UD2 (because of > UBSAN_TRAP). > > When I remove UBSAN_TRAP, the UD2s are replaced with calls to > __ubsan_handle_type_mismatch_v1().
Hrm, these are coming out of CONFIG_UBSAN_MISC, yes? It seems that the UBSAN checks that are non-recoverable all inject unreachable checks afterwards, from what I can see.
> Kees, any idea?
Isn't this another version of the earlier unreachable-ud2 issue?
Regardless, the type_mismatch it triggered for misalignment and object-size checks, and the alignment check is likely going to always misfire on x86. The randconfig includes that config:
CONFIG_UBSAN_ALIGNMENT=y
So perhaps the config should be strengthened to disallow it under COMPILE_TEST?
config UBSAN_ALIGNMENT def_bool !UBSAN_NO_ALIGNMENT depends on !COMPILE_TEST
-- Kees Cook
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