From: "Mattias Rönnblom" <hofors@lysator.liu.se>
To: Stephen Hemminger <stephen@networkplumber.org>, dev@dpdk.org
Cc: "Morten Brørup" <mb@smartsharesystems.com>,
"Bruce Richardson" <bruce.richardson@intel.com>,
"Konstantin Ananyev" <konstantin.v.ananyev@yandex.ru>,
"Zhihong Wang" <wangzhihong.wzh@bytedance.com>,
"Yuanhan Liu" <yliu@fridaylinux.org>,
"Xiaoyun Li" <xiaoyun.li@intel.com>
Subject: Re: [PATCH] rte_memcpy: fix off by one for size 16 and 32
Date: Sun, 3 Mar 2024 07:46:25 +0100 [thread overview]
Message-ID: <e6080e25-c6a3-4aa4-9585-ec6df61d4ce1@lysator.liu.se> (raw)
In-Reply-To: <20240302125647.63ef6aec@hermes.local>
On 2024-03-02 21:56, Stephen Hemminger wrote:
> On Sat, 2 Mar 2024 12:49:23 -0800
> Stephen Hemminger <stephen@networkplumber.org> wrote:
>
>> The rte_memcpy code would do extra instructions for size 16
>> and 32 which potentially could reference past end of data.
>>
>> For size of 16, only single mov16 is needed.
>> same for size of 32, only single mov32.
>>
>> Fixes: f5472703c0bd ("eal: optimize aligned memcpy on x86")
>> Fixes: d35cc1fe6a7a ("eal/x86: revert select optimized memcpy at run-time")
>>
>> Suggested-by: Morten Brørup <mb@smartsharesystems.com>
>> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
>
> Self-NAK, more is needed here.
>
> The code has lots of pre-existing bugs where it will reference past the end
> of the data in some cases.
Memory beyond the buffer is not accessed in this case. The rte_mov16()
copies just overlap.
A colleague pointed out the same "bug" to me a couple of years ago. We
didn't realize what code would be generated in the n == 16 case though.
That seems very much worth fixing.
Maybe it's worth adding a comment regarding the overlap.
next prev parent reply other threads:[~2024-03-03 6:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-02 20:49 Stephen Hemminger
2024-03-02 20:56 ` Stephen Hemminger
2024-03-02 22:10 ` Morten Brørup
2024-03-03 6:46 ` Mattias Rönnblom [this message]
2024-03-02 23:57 ` Morten Brørup
2024-03-03 6:47 ` Mattias Rönnblom
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