Re: Bug: "perf record" reporting buffer overflow when writing data

[Yang Jihong]

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.