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From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-kernel@vger.kernel.org,
	Randy Dunlap <rdunlap@infradead.org>,
	aryabinin@virtuozzo.com, dvyukov@google.com,
	keescook@chromium.org
Subject: Re: [PATCH] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings, again
Date: Mon, 4 Jan 2021 16:13:17 +0100	[thread overview]
Message-ID: <20210104151317.GR3021@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <590998aa9cc50f431343f76cae72b2abf8ac1fdd.1608699683.git.jpoimboe@redhat.com>

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+ ?

  parent reply	other threads:[~2021-01-04 15:15 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-23  5:04 Josh Poimboeuf
2020-12-23  7:18 ` Randy Dunlap
2021-01-07 10:06   ` David Laight
2021-01-04 15:13 ` Peter Zijlstra [this message]
2021-01-06 23:37   ` Kees Cook
2021-01-07  0:06     ` Randy Dunlap
2021-01-07 21:07       ` Kees Cook
2021-01-13 23:27         ` Josh Poimboeuf
2021-01-07 10:51     ` Dmitry Vyukov
2021-01-14 10:59   ` [PATCH] ubsan: Require GCC-8+ or Clang to use UBSAN Peter Zijlstra
2021-01-14 11:09     ` Andrey Ryabinin
2021-01-18 17:53       ` Josh Poimboeuf
2021-02-09 18:24         ` Josh Poimboeuf
2021-02-09 23:17           ` Andrey Rybainin
2021-02-10  0:21             ` Kees Cook

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