Messages in this thread | | | Date | Thu, 7 Jan 2021 09:22:00 -0800 | From | Kees Cook <> | Subject | Re: [PATCH] ubsan: disable unsigned-integer-overflow sanitizer with clang |
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On Thu, Jan 07, 2021 at 05:09:59PM +0100, Arnd Bergmann wrote: > On Wed, Jan 6, 2021 at 11:12 PM Arnd Bergmann <arnd@kernel.org> wrote: > > > > On Wed, Jan 6, 2021 at 10:57 PM Kees Cook <keescook@chromium.org> wrote: > > > On Wed, Dec 30, 2020 at 04:47:35PM +0100, Arnd Bergmann wrote: > > > > diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan > > > > index 8b635fd75fe4..e23873282ba7 100644 > > > > --- a/lib/Kconfig.ubsan > > > > +++ b/lib/Kconfig.ubsan > > > > @@ -122,6 +122,8 @@ config UBSAN_SIGNED_OVERFLOW > > > > > > > > config UBSAN_UNSIGNED_OVERFLOW > > > > bool "Perform checking for unsigned arithmetic overflow" > > > > + # clang hugely expands stack usage with -fsanitize=object-size > > > > + depends on !CC_IS_CLANG > > > > depends on $(cc-option,-fsanitize=unsigned-integer-overflow) > > > > > > Because of Clang implementation issues (see commit c637693b20da), this is > > > already "default n" (and not supported under GCC at all). IIUC, setting > > > this to "depends on !COMPILE_TEST" won't work for randconfigs, yes? > > > > Ah, I had not realized this is clang specific. Adding the !COMPILE_TEST > > dependency would hide it for me, which may be good enough for me. > > > > > Is there some better way to mark this as "known to have issues, please > > > don't include in randconfig?" > > > > > > I'd like to keep it around so people can continue to work out the > > > problems with it, but not have unexpecting folks trip over it. ;) > > > > I've reverted that patch locally now and default-enabled for randconfigs. > > Now that I have an otherwise clean build, this should provide me > > with a full set of files that produce the warning. If the number is > > small enough, I could try opening individual github issues. > > A day's worth of randconfig builds with clang-11 or clang-12 shows these > instances that exceeded the warning limit: > > crypto/blake2b_generic.c:98:13: error: stack frame size of 9636 bytes > in function 'blake2b_compress' [-Werror,-Wframe-larger-than=] > crypto/sha512_generic.c:151:13: error: stack frame size of 1292 bytes > in function 'sha512_generic_block_fn' [-Werror,-Wframe-larger-than=] > lib/crypto/curve25519-fiat32.c:312:22: error: stack frame size of 2180 > bytes in function 'fe_mul_impl' [-Werror,-Wframe-larger-than=] > lib/crypto/curve25519-fiat32.c:444:22: error: stack frame size of 1588 > bytes in function 'fe_sqr_impl' [-Werror,-Wframe-larger-than=] > fs/btrfs/scrub.c:3028:31: error: stack frame size of 1132 bytes in > function 'scrub_stripe' [-Werror,-Wframe-larger-than=] > drivers/net/ethernet/intel/e1000/e1000_main.c:3590:6: warning: stack > frame size of 1100 bytes in function 'e1000_update_stats' > [-Wframe-larger-than=] > drivers/net/ethernet/broadcom/tg3.c:11829:13: warning: stack frame > size of 1188 bytes in function 'tg3_get_estats' [-Wframe-larger-than=] > drivers/net/ethernet/intel/igb/igb_main.c:6551:6: warning: stack frame > size of 1348 bytes in function 'igb_update_stats' > [-Wframe-larger-than=] > drivers/net/ethernet/intel/igc/igc_main.c:3608:6: warning: stack frame > size of 1124 bytes in function 'igc_update_stats' > [-Wframe-larger-than=] > drivers/net/ethernet/qlogic/qed/qed_l2.c:1759:1: warning: stack frame > size of 1300 bytes in function '__qed_get_vport_port_stats' > [-Wframe-larger-than=] > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c:7022:6: warning: stack > frame size of 1564 bytes in function 'ixgbe_update_stats' > [-Wframe-larger-than=] > drivers/net/ethernet/intel/ixgb/ixgb_main.c:1590:1: warning: stack > frame size of 1140 bytes in function 'ixgb_update_stats' > [-Wframe-larger-than=] > drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.c:145:6: warning: > stack frame size of 1068 bytes in function 'mlx5i_get_stats' > [-Wframe-larger-than=] > drivers/staging/media/atomisp/pci/atomisp_cmd.c:5600:5: warning: stack > frame size of 1052 bytes in function 'atomisp_set_fmt' > [-Wframe-larger-than=] > > All of these *only* happen on 32-bit x86, and can be reproduced in a > i386_defconfig, with the corresponding drivers (btrfs, sha512, blake2b, > curve25519, and the ethernet ones) and UBSAN_UNSIGNED_OVERFLOW > manually enabled. Given that few people still care about i386, maybe > we could just make the option depend on !CONFIG_X86_32
I'm fine with that -- or maybe any 32-bit architecture, if the problem is poor stack space optimization on 32-bit archs?
> > That config also runs into two more BUILD_BUG_ON() that I had not > seen in randconfig tests: > > (i386 defconfig plus ubsan) > ld.lld: error: undefined symbol: __compiletime_assert_207 > >>> referenced by cpu_entry_area.c > >>> mm/cpu_entry_area.o:(setup_cpu_entry_area_ptes) in archive arch/x86/built-in.a
That one I don't think I've seen before.
> > (x86-64 defconfig plus ubsan) > ld.lld: error: undefined symbol: __compiletime_assert_362 > >>> referenced by efi_64.c > >>> platform/efi/efi_64.o:(efi_sync_low_kernel_mappings) in archive arch/x86/built-in.a
I think this is: https://github.com/ClangBuiltLinux/linux/issues/256 and that bug needs re-opening? Or maybe there's a new bug I can't find?
-- Kees Cook
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