Messages in this thread | | | Subject | Re: [PATCH] ubsan: Require GCC-8+ or Clang to use UBSAN | From | Andrey Rybainin <> | Date | Wed, 10 Feb 2021 02:17:57 +0300 |
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On 2/9/21 9:24 PM, Josh Poimboeuf wrote: > On Mon, Jan 18, 2021 at 11:53:37AM -0600, Josh Poimboeuf wrote: >> On Thu, Jan 14, 2021 at 02:09:28PM +0300, Andrey Ryabinin wrote: >>> >>> >>> 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. >> >> Is that preferable? Always happy to remove code, just need some >> justification behind it. > > Andrey, > > Is Peter's patch acceptable or do you want to do something else? >
I do prefer to just remove the code, I'll send the patch shortly.
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