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Message-ID: <7d7b94ba-9a1f-44de-8491-dc4864338f80@embeddedor.com>
Date: Tue, 9 Jan 2024 06:31:41 -0600
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Subject: Re: [PATCH v2 2/2] VMCI: Fix memcpy() run-time warning in
 dg_dispatch_as_host()
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To: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Kees Cook <keescook@chromium.org>,
 Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>,
 linux-hardening@vger.kernel.org, error27@gmail.com, gustavoars@kernel.org,
 Bryan Tan <bryantan@vmware.com>, Vishnu Dasa <vdasa@vmware.com>,
 VMware PV-Drivers Reviewers <pv-drivers@vmware.com>,
 Arnd Bergmann <arnd@arndb.de>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 linux-kernel@vger.kernel.org, vegard.nossum@oracle.com,
 darren.kenny@oracle.com, syzkaller <syzkaller@googlegroups.com>
References: <20240105164001.2129796-1-harshit.m.mogalapalli@oracle.com>
 <20240105164001.2129796-2-harshit.m.mogalapalli@oracle.com>
 <202401081430.9DAB37B46@keescook>
 <9c742547-0021-464b-b7a8-7af46b0a4afa@embeddedor.com>
 <79ca2f85-1f8d-4a12-aa5a-09137033605f@moroto.mountain>
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
In-Reply-To: <79ca2f85-1f8d-4a12-aa5a-09137033605f@moroto.mountain>
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On 1/9/24 03:07, Dan Carpenter wrote:
> On Mon, Jan 08, 2024 at 08:05:38PM -0600, Gustavo A. R. Silva wrote:
>>>> Gustavo quoted:
>>>> "Under FORTIFY_SOURCE we should not copy data across multiple members
>>>> in a structure."
>>>>
>>>> Reported-by: syzkaller <syzkaller@googlegroups.com>
>>>> Suggested-by: Vegard Nossum <vegard.nossum@oracle.com>
>>>> Suggested-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>>> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
>>>
>>> Thanks for getting this fixed!
>>>
>>> Yeah, it's a "false positive" in the sense that the code was expecting
>>
>> It's a false positive _bug_, and a legitimate _warning_ coming from fortified
>> memcpy().
> 
> It really feels like you're trying to sell the cost of this as a good
> thing...  We've already merged fortify so why are you still fighting

No, I'm just describing (here[1] and below), clear and concise, what fortify
is doing in this particular case, in response to your first intervention
in this thread[3].

"The warning is triggered because of a write beyond the boundaries of
`dg_info->msg`."[2]

You're arguing that fortify caused a problem. I'm describing the reason
why the feature triggered the warning. That's it, I guess.

Thanks
--
Gustavo

[1] https://lore.kernel.org/linux-hardening/9c742547-0021-464b-b7a8-7af46b0a4afa@embeddedor.com/
[2] https://lore.kernel.org/linux-hardening/7826922a-d642-424e-bede-bfc45be9254d@embeddedor.com/
[3] https://lore.kernel.org/linux-hardening/fc132bde-d42d-4aac-ba91-7a939a18091a@moroto.mountain/