Messages in this thread | | | Date | Wed, 6 Jan 2021 15:37:53 -0800 | From | Kees Cook <> | Subject | Re: [PATCH] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings, again |
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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+ ?
I would be totally fine with that. The only thing I can think of that might care is syzbot. Dmitry, does syzbot use anything older than gcc 8?
-- Kees Cook
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