From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>,
"Darrick J . Wong" <djwong@kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -next 1/1] iomap: Fix a false positive of UBSAN in iomap_seek_data()
Date: Mon, 5 Jul 2021 11:35:08 +0800 [thread overview]
Message-ID: <492c7a7b-6f2e-de45-c733-51c80422305e@huawei.com> (raw)
In-Reply-To: <YN9vZfo+84gizjtf@casper.infradead.org>
On 2021/7/3 3:56, Matthew Wilcox wrote:
> On Fri, Jul 02, 2021 at 05:21:09PM +0800, Zhen Lei wrote:
>> Move the evaluation expression "size - offset" after the "if (offset < 0)"
>> judgment statement to eliminate a false positive produced by the UBSAN.
>>
>> No functional changes.
>>
>> ==========================================================================
>> UBSAN: Undefined behaviour in fs/iomap.c:1435:9
>> signed integer overflow:
>> 0 - -9223372036854775808 cannot be represented in type 'long long int'
>
> I don't understand. I thought we defined the behaviour of signed
> integer overflow in the kernel with whatever-the-gcc-flag-is?
-9223372036854775808 ==> 0x8000000000000000 ==> -0
I don't fully understand what you mean. This is triggered by explicit error
injection '-0' at runtime, which should not be detected by compilation options.
lseek(r1, 0x8000000000000000, 0x3)
>
>
> .
>
next prev parent reply other threads:[~2021-07-05 3:35 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-02 9:21 [PATCH -next 1/1] iomap: Fix a false positive of UBSAN in iomap_seek_data() Zhen Lei
2021-07-02 9:34 ` Christoph Hellwig
2021-07-02 11:50 ` Leizhen (ThunderTown)
2021-07-05 3:29 ` Leizhen (ThunderTown)
2021-07-05 3:43 ` Matthew Wilcox
2021-07-05 4:05 ` Leizhen (ThunderTown)
2021-07-04 13:51 ` Matthew Wilcox
2021-07-02 19:56 ` Matthew Wilcox
2021-07-05 3:35 ` Leizhen (ThunderTown) [this message]
2021-07-06 11:08 ` Matthew Wilcox
2021-07-06 11:59 ` Matthew Wilcox
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