Messages in this thread | | | Subject | Re: [PATCH] ubsan: Require GCC-8+ or Clang to use UBSAN | From | Andrey Ryabinin <> | Date | Thu, 14 Jan 2021 14:09:28 +0300 |
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On 1/14/21 1:59 PM, Peter Zijlstra wrote: > On Mon, Jan 04, 2021 at 04:13:17PM +0100, Peter Zijlstra wrote: >> On Tue, Dec 22, 2020 at 11:04:54PM -0600, Josh Poimboeuf wrote: >>> GCC 7 has a known bug where UBSAN ignores '-fwrapv' and generates false >>> signed-overflow-UB warnings. The type mismatch between 'i' and >>> 'nr_segs' in copy_compat_iovec_from_user() is causing such a warning, >>> which also happens to violate uaccess rules: >>> >>> lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to __ubsan_handle_add_overflow() with UACCESS enabled >>> >>> Fix it by making the variable types match. >>> >>> This is similar to a previous commit: >>> >>> 29da93fea3ea ("mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions") >> >> Maybe it's time we make UBSAN builds depend on GCC-8+ ? > > --- > Subject: ubsan: Require GCC-8+ or Clang to use UBSAN > > Just like how we require GCC-8.2 for KASAN due to compiler bugs, require > a sane version of GCC for UBSAN. > > Specifically, before GCC-8 UBSAN doesn't respect -fwrapv and thinks > signed arithmetic is buggered. >
Actually removing CONFIG_UBSAN_SIGNED_OVERFLOW would give us the same effect without restricting GCC versions.
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