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Subject: Re: Bug: "perf record" reporting buffer overflow when writing data
To:     Will Ochowicz <Will.Ochowicz@genusplc.com>,
        "linux-perf-users@vger.kernel.org" <linux-perf-users@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <CWLP265MB497033A5B448268D677F03DD9C649@CWLP265MB4970.GBRP265.PROD.OUTLOOK.COM>
 <6c88ac58-a2c8-0b15-a106-9c8b0e26b3ac@huawei.com>
 <CWLP265MB4970C9D9667C9419567243409C659@CWLP265MB4970.GBRP265.PROD.OUTLOOK.COM>
From:   Yang Jihong <yangjihong1@huawei.com>
Message-ID: <2a7fd858-1639-53a7-bc65-d4f65a9eed2f@huawei.com>
Date:   Thu, 27 Apr 2023 09:18:49 +0800
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Hello,

On 2023/4/26 20:52, Will Ochowicz wrote:
> Hi Yang,
> 
>  1. Displaying notes found in: .note.gnu.build-id
>        Owner                Data size        Description
>        GNU                  0x00000028       NT_GNU_BUILD_ID (unique
>     build ID bitstring)
>          Build ID:
>     6236326637343061343961353463366632643232333465366562353039656634
>     3938656130663039
> 
>  2. That patch did fix the issue.
Thanks for your test to help confirm the problem.
I'll send a fix patch.

> 
> Would you mind giving me a quick explanation of the issue for my own 
> edification?
> 
According to the coredump stack trace, the following code causes the 
out-of-bounds access problem:

#7  0x00005555557e7ddd in memcpy (__len=40, __src=0x555556a28b38, 
__dest=0x7fffffff843c)      at 
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:29
#8  write_buildid (fd=0x7fffffff8590, misc=<optimized out>, pid=-1, 
bid=0x555556a28b38,      name_len=<optimized out>, name=0x555556a28c0c 
"/opt/pylon/lib/libpylonbase-6.1.1.so") at util/build-id.c:312

That is, an error occurred when writing the build_id of the 
"/opt/pylon/lib/libpylonbase-6.1.1.so" file.

The corresponding code is as follows:

write_buildid()
{
   ...
   memcpy(&b.data, bid->data, bid->size);
   ...
}

b.data is an array whose size is Build_ID_SIZE(20), but bid->size is 
greater than this value. Check the perf code and find this problem.

Thanks,
Yang.