Messages in this thread | | | Subject | Re: [PATCH] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings, again | From | Randy Dunlap <> | Date | Wed, 6 Jan 2021 16:06:57 -0800 |
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On 1/6/21 3:37 PM, Kees Cook 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+ ? > > 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?
I use UBSAN successfully with GCC 7.5.0. However, I can revert whatever future patch someone adds for this...
-- ~Randy
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